Kids Cube/7_Science.iso/dc13/dc.doc

Text File | 1994-04-01 | 89KB | 1,735 lines

                            DC CIRCUIT ANALYSIS
                          Version 1.3, March 1994
                   Copyright 1991-1994, Arthur Tanzella
                            All Rights Reserved

The "DC Circuit Analysis" program is intended as an educational tool for
introducing the user to the concepts of Direct Current (DC) circuits in
general, and digital computer circuits in particular.  Circuits can be
created and evaluated on the computer screen.  This program is not intended
to be a design tool, and as such does not properly handle some analog
circuits, such as operational amplifiers.  This documentation can function
as a tutorial to learn about semiconductors, logic, and digital computer
circuits.  Numerous sample circuits are used throughout this documentation
and can be displayed and evaluated using this program.

ACKNOWLEDGEMENTS

I would like to take this opportunity to thank the following people who are
my good friends, and have contributed significantly to this program.  Their
contributions were in the testing of the program and in the form of their
suggestions to make this program and this documentation easier to use and
read.

                Warren Cella
                Ken Hanawalt
                Art Silverstein
                Mike Weisfield
                Bill Locke

I would also like to thank Bill Locke for contributing subroutines to solve
a matrix of simultaneous equations.

LICENSE AGREEMENT

DC Circuit Analysis is a "Shareware Program" and is provided at no charge
to the user for a one week evaluation period.  Feel free to share it with
your friends, but please do not give it away altered or as part of another
system.  The essence of "user-supported" software is to provide personal
computer users with quality software without high prices, and yet to
provide incentive for programmers to continue to develop new products.  If
you find this program useful and continue to use the program after the one
week evaluation period, you are requested to send a registration payment of
$15 (US) to:

                Arthur Tanzella
                4613 Clubvue Drive
                Pittsburgh, PA 15236-4803
                USA

Print out and fill in the "REGISTER.DOC" file.  Send it with the $15 (US)
registration fee to the above address to register this program.

The $15 (US) registration fee will license one copy for use on any one
computer at any one time.  You must treat this software just like a book.
An example is that this software may be used by any number of people and
may be freely moved from one computer location to another, so long as there
is no possibility of it being used at one location while it's being used at
another.  Treat the software just like a book that cannot be read by two
people in two different locations at the same time.

Users of DC Circuit Analysis must accept this disclaimer of warranty: "DC
Circuit Analysis is supplied as is.  The author disclaims all warranties,
expressed or implied, including, without limitation, the warranties of
merchantability and of fitness for any purpose. The author assumes no
liability for damages, direct or consequential, which may result from the
use of DC Circuit Analysis."

Commercial users of DC Circuit Analysis must register and pay for their
copies of DC Circuit Analysis within 30 days of first use or their license
is withdrawn.  Site-License arrangements may be made by contacting Arthur
Tanzella at the above address.

Anyone distributing DC Circuit Analysis for any kind of remuneration must
first contact Arthur Tanzella at the address above for authorization. This
authorization will be automatically granted to distributors recognized by
the Association of Shareware Professionals (ASP) as adhering to its
guidelines for shareware distributors, and such distributors may begin
offering DC Circuit Analysis immediately.  However, Arthur Tanzella must
still be advised so that the distributor can be kept up-to-date with the
latest version of the DC Circuit Analysis program.

You are encouraged to pass a copy of DC Circuit Analysis along to your
friends for evaluation.  Please encourage them to register their copy if
they plan to continue using it.  All registered users will receive a copy
of the latest version of the DC Circuit Analysis program when they
register.  If you have any comments or problems with this program, you can
contact me at the address above.  Support will be provided to all
registered users for a minimum of three months from the time they
registered.

ASP OMBUDSMAN

This program is produced by a member of the Association of Shareware
Professionals (ASP).  ASP wants to make sure that the shareware principle
works for you.  If you are unable to resolve a shareware-related problem
with an ASP member by contacting the member directly, ASP may be able to
help.  The ASP Ombudsman can help you resolve a dispute or problem with an
ASP member, but does not provide technical support for members' products.
Please write to the ASP Ombudsman at 545 Grover Road, Muskegon, MI 49442 or
send a CompuServe message via CompuServe Mail to ASP Ombudsman 70007,3536.

GETTING STARTED

The DC Circuit Analysis program contains over 100 files occupying
approximately 800 KB of disk space, and is compressed into a single self-
extracting file called "INSTALL.EXE."  This file was created using the
LHarc version 2.11 program, which is a copyright reserved freeware program
written by Haruyasu Yoshizaki.

To run the program requires a 286 or later (386, 486, or Pentium)
processor, an EGA or VGA graphics adapter with 256 KB of RAM installed, and
a color monitor.  It also requires between 300 KB and 350 KB of available
RAM after DOS, drivers and Terminate and Stay Resident (TSR) program are
loaded.  The actual amount of RAM required depends on the complexity of the
circuit.  If Expanded Memory (EMS) is installed, only 300 KB of RAM is
required.  You can use the CHKDSK or MEM command to determine if you have
enough available RAM to run this program.

To start the DC Circuit Analysis you must be in the directory containing
this program.  Typically, the program is stored in the C:\DC13 directory.
Use the DOS "CD" (Change Directory) command to change the default directory
to the program directory as follows:

                CD \DC13

To start the program type "DC"  with or without parameters as follows:

                DC
                   or
                DC filename.DC
                   or
                DC filename.DC x

If no parameters are specified after the "DC" command, the opening (help)
screen of the on-line tutorial will be displayed.  This tutorial contains
all the information in this document, and allows access in a Hyper-Text
like fashion.  The cursor keys (or mouse) can be used to highlight keywords
on the screen.  The ENTER key will display another screen of information
whose subject corresponds to the selected keyword.  The PGDN key, or
selecting the "More" keyword, will display the next screen of information.
The PGUP key will display the previous screen.  The F1 key will display the
first screen of the tutorial.  From the first screen the "Table of
Contents" keyword will display a screen containing the Table of Contents
that will allow you to jump directly to the desired section.  The "Index"
keyword will display a screen containing many different keywords.  The ESC
key will exit the Tutorial and return you to the DC Circuit Analysis
program.  The F5 key will allow you to return to the tutorial at the same
screen previously displayed.

Upon exiting the tutorial, the program will display a menu containing the
directory of sample circuits in alphabetical order.  The PGUP and PGDN key
will page through this directory.  The UP and DOWN key will highlight
sample circuits in the current page, and the ENTER key will select the
highlighted sample circuit file.  F10 or ESC will exit this menu without
selecting a sample circuit.  At the opening menu you can select "Exit" to
exit the program without modifying the sample circuit.

If a filename is specified on the command line, and it does not exist, the
program will display the "Modify Circuit" screen which allows you to create
a new circuit.  By convention, circuit files have the extension "DC."
Press F10 or ESC to exit this screen.  When exiting from the opening menu
you can choose to Save the Circuit or Exit without saving the circuit.  If
you choose to save the circuit, it will be stored in the file (filename.DC)
specified on the command line when you started the program.  If a problem
occurs during the writing of the file, you will be prompted to enter a new
filename.

If the file specified on the command line already exist, the program will
display the opening menu.  Your choices are:

                Analyze Circuit
                Modify Circuit
                Select Sample Circuit
                Save Circuit As
                Save Circuit
                Exit
"Analyze Circuit" will evaluate the circuit, calculating, and displaying
voltages at interconnect nodes.  It will also calculate and display the
current and its direction across each resistor in the circuit.  Finally, it
will determine if any components are overloaded.

If you want to analyze a circuit and exit without modifying the circuit,
add any character following the filename on the command line as follows:

                DC filename.DC x

Sample circuit files are located in the "DC" sub-directory under the
default directory.  You must prefix sample filenames with "DC\" to access
files in this sub-directory as follows:

                DC DC\filename.DC x

As an example, let's look at the "RESIST1.DC" sample circuit.  Type the
following:

                DC DC\RESIST1.DC R

Or you can enter the program without specifying a filename, and select
"RESIST1.DC" from the select sample circuit menu.  Next select "Analyze
Circuit" from the opening menu.

This file actually contains three separate resistor circuits.  The simplest
circuit is on the left, and the circuits gradually become more complex as
you move to the right.  Notice that voltages at interconnect nodes are
displayed in green, and currents across resistors are displayed in orange.
Further notice, that an arrow prefixes the current indicating the direction
of the current, always pointing from a larger voltage to a smaller voltage.
The ESC or F10 key is used to exit.

BASIC ELECTRICAL THEORY

Electrical potential is measured in Volts (V).  Electrical current is
measured in Amperes or Amps (A).  Electrical resistance is measured in
Ohms (Ω).  Electrical power is measured in Watts (W).

Conductors are usually metal wires made of copper or aluminum, and are used
to conduct electricity.  These metals have a very small resistance measured
in milliohms (0.001 ohms) per foot of wire, depending on the diameter of
the wire.  The DC Circuit Analysis program assumes that wires used to
connect components have zero resistance.  This assumption is valid if short
distances (less than a few feet) are involved.

Insulators are usually made of materials like rubber and plastic, and are
used to insulate wires.  Insulators have very high resistances (millions of
ohms).

Resistors are components that allow electrical current to flow, but resist
the current converting some of it into heat.  Resistors are typically made
from carbon, and have resistances measured in ohms or Killohms (1000 ohms).

A potentiometer is a variable resistor with three connection points.  The
top and bottom connections are to a fixed resistor.  The middle connection
can make contact at different locations along this resistor.  Hence, the
sum of the resistance between the middle connection and the top connection,
and the resistance between the middle connection and the bottom connection,
is the same as the resistance between the top and the bottom connection.
Other basic electrical components include capacitors and inductors.
Capacitors are constructed of two large surface area conductors separated
by a thin insulator.  Capacitors are typically used in an Alternating
Current (AC) circuit to filter selective frequencies.  They can also be
used to stabilize a DC voltage from voltage spikes.

Inductors are wires wrapped into a coil.  When electrical current spirals
through an inductor it creates a magnetic field.  Inductors are primarily
used in AC circuits to produce oscillators.  Inductors have the opposite
effect of capacitors on a circuit.  Inductors can also be used to create
electromagnets.  If two inductors are wrapped around the same iron core,
they form a transformer.  Transformers are used to raise or lower AC
voltages.

It is possible to create an electrical potential by passing an inductor
through a magnetic field.  This is how an electrical generator works.

Batteries are electrical devices that use chemicals to produce an
electrical potential.  The battery has an excess of electrons (negatively
charged) at its negative pole, and a shortage of electrons at its positive
pole.

Both generators and batteries can be used to supply power to an electrical
circuit.  This program represents the power supply using fixed voltage
nodes established at +10V, +5V, 0V (ground), -5V, or -10V.

In a steady state DC circuit, capacitors act like an insulator, unless the
DC voltage is in excess of the capacitor rated voltage.  Inductors on the
other hand, act like wires or resistors with small resistance values.  For
this reason, the DC Circuit Analysis program does not support capacitors,
inductors or transformers.

This program assumes a steady state DC circuit and uses the following
equation to calculate voltage and current through out the circuit:

                V = I R

where:
        V is the potential measured in Volts
        I is the current measured in Amps
        R is the resistance measured in Ohms

Every component in the circuit is reduced to its characteristic resistance,
and the voltage potential across the component is calculated based on the
current flow using this equation.

The actual equation implemented in DC Circuit Analysis is a derivation of
V=IR for multiple resistors connected to the same node.  The assumption is
that the total current entering a node is equal to the total current
exiting that node (ΣI=0).   The following equation is used to calculate the
voltage at each node:

                      N
                      Σ Vi/Ri
                     i=0
                V = ──────────
                      N
                      Σ 1/Ri
                     i=0

where:
        V  is the calculated voltage at a specified node
        N  is the number of resistors connected to that node
        Ri is the resistance of each resistor
        Vi is the voltage at the node on the other end of each resistor

A double precision matrix of simultaneous equations is used to calculate
the voltage at each node.  The effective resistance of each semiconductor
is calculated based on the voltage at each node.  The calculation is
continually repeated until the voltage at each node converges (barely
changes).  The convergence criteria used by the program is a function of
the speed of the computer.  The convergence criteria ranges from a
stringent value of 1.0e-10 (0.0000000001) Volts for fast computers, to a
relaxed value of 1.0e-8 (0.00000001) Volts for slow computers.  The more
stringent the convergence criteria the longer this program may take to
calculate voltage and current, and the more accurate the results are.  You
can override the convergence value and explicitly set it external to the
program using the DOS environmental variable "DC_DV" as follows:

                SET DC_DV=1.0e-8

Electrical power is calculated using the following equation:

                P = V I
                  or
                P = I² R

where:
        P  is the calculated power in Watts
        V  is the potential across a component measured in Volts
        I  is the current passing through the component measured in Amps
        I² is the current squared (current multiplied by itself) in Amps²
        R  is the resistance of the component measured in Ohms

Power is calculated to determine if various components are overloaded.  All
resistors in the library are assumed to be standard ¼ Watt resistors.  As
an example, using the equation I = V/R, an 100 ohm resistor connected to a
10 Volt source and ground has a current of 0.1 Amps passing through it.
Using the power equation P = VI, the power through this resistor is 1 Watt
which exceeds its rated value of a ¼ Watt.  Hence, this component
(resistor) is overloaded.

USING THE PROGRAM

The DC Circuit Analysis program will automatically detect and uses the
following: a math coprocessor, a two or three button mouse, and EMS
(Expanded) memory.  These items are not required, but if found, will
improve the performance of the program.

DC Circuit Analysis supports a mouse if one is installed with either the
MOUSE.SYS or MOUSE.COM driver.  However, a mouse is not required.  In
general, the left mouse button is equivalent to the ENTER key and is used
to select items.  The right mouse button is equivalent to the ESC key and
is used to exit screens.  If the mouse has three buttons, the middle button
is supported in the Select Sample Circuit screen to page through the
directory, in the Modify Circuit screen to display the Library of
Components screen, and to switch pages of library components.

Let us now analyze the "RESIST2.DC" sample circuit.  This file contains two
sample circuits, one with a potentiometer, and the other with a switch.
When more than one adjustable component (Switch or Potentiometer) is in a
circuit, the LEFT and RIGHT cursor keys are used to select an adjustable
component.  Adjustable components with blue back grounds indicate they have
been selected.  If a mouse is installed, it can be used to select an
adjustable component.  The ENTER key or the left mouse button will toggle
the selected switch, or increment the selected potentiometer in 10%
increments.

All switches are Single-Pole Double-Throw.  When a switch is selected, the
HOME, PGUP, and UP cursor keys will position the switch in the up position.
The END, PGDN, and DOWN cursor keys will position the switch in the down
position.

When a potentiometer is selected, the UP and DOWN cursor keys will
increment or decrement the potentiometer in 1% increments.  The PGUP and
PGDN keys will increment or decrement the potentiometer in 10% increments.
The HOME key sets the potentiometer to 99%, and the END key sets it to 1%.

If a potentiometer in the circuit is selected, the "p" key will plot a
graph of the first eight interconnect node voltages (labeled A through H in
yellow) versus the potentiometer voltage.  The program will automatically
calculate voltages at every node as it adjusts the potentiometer.  If you
have a fast computer, the potentiometer will be adjusted in 1% increments
from 1% to 99%.  Slower computers will use larger increments between 2% and
5%.  Since the program must continually calculate the circuit until it
converges for each time the potentiometer is incremented, plots can take up
to ten minutes, depending on the complexity of the circuit and the speed of
the computer.  A math coprocessor can speed up the calculation, but is not
required.  The DOS environmental variable "DC_PLOT" can be used to
explicitly set the potentiometer increments external to the program as
follows:

                SET DC_PLOT=5

Once the program completes this calculation, the plot will be displayed on
the screen.  Press any key to exit the plot and return to the analysis
screen.  Subsequent "p" commands will instantly redisplay the plot without
recalculation.  Hence, you can press "p" to toggle between the plot and the
analysis screen.  You can also adjust the potentiometer on the analysis
screen as you toggle between the two screens.

Interconnect nodes, that are connected to fixed voltage or switches, are
treated as though they are fixed nodes with the corresponding voltage,
hence the program does not explicitly display a voltage adjacent to these
nodes.  Interconnect nodes that are connected to other interconnect nodes
are combined for calculational purposes into a single interconnect node and
the calculated voltage is displayed only at the node that was created
first.
Finally, the "w" key writes the Analysis or Plot screen into a PC
Paintbrush compatible file called DC.PCX.  If the DOS environmental
variable TMP is defined, the DC.PCX file will be written to the directory
identified by the TMP variable, otherwise it will be written to the default
directory.

Now let's exit (ESC) this sample circuit and look at modifying a circuit.

Let's start with the existing circuit RESIST1.DC.  After selecting this
circuit from the "Select Sample Circuit" menu, you should save it under a
different name using the "Save Circuit As" menu.  To modify the circuit you
should select "Modify Circuit" from the opening menu.

Now let's modify the first circuit on the left.  Let's change the 10V fixed
voltage node to 5V fixed voltage node.  Use the cursor keys or the mouse to
move the cursor over the 10V fixed voltage icon.  Hold the CTRL key and the
BACKSPACE key down simultaneously to delete the 10V fixed voltage icon.
Now press F4, or the middle button on the mouse, to display the library of
components.  If you have a slow disk drive, it may take a few seconds to
display this screen, because it must read the library file containing the
icons.  A 256 KB disk cache, such as SMARTDRV (see your MS-DOS manual),
would speed up the display of this screen.  Use the cursor keys or mouse to
move the white box to the 5V fixed voltage icon.  Press ENTER or the left
mouse button to select this icon.  The Modify Circuit screen will now
reappear.  Use the cursor keys or mouse to move the icon to the same
location that the 10V fixed voltage icon was in, and press ENTER or the
left mouse button to lock it in place.

Beware that if you attempt to locate the icon too close to an existing icon
on the screen, you will get the message: "ERROR - Component Overlaps
Another Component."  If this occurs, press any key to clear the message,
move the icon to another location, and press ENTER or the left mouse
button.  Icons must have some space between them.  They cannot be touching.
Think of each icon as having an invisible rectangular outline that
encompass the icon.

If you need to move an icon, locate the cursor on top of the icon and press
the F3 key.  Then use the cursor keys or mouse to move the icon to a new
location and press ENTER or the left mouse button to lock it in place.

We now must connect the 5V fixed voltage node to the top of the resistor.
Locate the cursor over the bottom circle (connection point) of the 5V fixed
voltage node, and press ENTER or the left mouse button.  The icon will turn
red.  Now locate the cursor over the top portion of the resistor and press
ENTER or the left mouse button.  The program will draw a wire (line)
between the two connection points.  You must always select a node
(interconnect, fixed, or switch) before selecting a component (or IC) to
make a connection.  You can use the same procedure to disconnect (remove) a
wire.  You can connect two nodes together in any order.

You can press F1 for a brief help message.  For additional help, press F1 a
second time to receive a full screen of help.  This screen identifies the
different types of nodes and components in the library.

Finally, press F6 to analyze the circuit and see the results of your
modification.  F6 allows you to switch between the "Analyze Circuit" and
"Modify Circuit" screens.

Now is a good time for you to attempt to build your first circuit from
scratch.  Exit the program and type the following:

                DC DC\TEST2.DC

Now build a simple resistor circuit of your choosing.  Then proceed to
analyze your circuit.

Lets look at the RESIST3.DC sample circuit for an example of a complex
resistor network.

BASIC SEMICONDUCTOR THEORY

In addition to resistors, there are electrical components called
semiconductors.  They get their name from the fact that sometimes they act
as a conductor, a resistor, or an insulator depending on the circumstance.
Semiconductors are typically made of materials like silicon or germanium.

There are two types of semiconductor materials, Positive type (P-type)
material, and Negative type (N-type) material.  Typically, a semiconductor
starts with a chemical group IV element (with four outer electrons), such
as silicon.   This material must be formed into a nearly perfect crystal.
A small quantity of a group III element (with three outer electrons), such
as boron, is added to create P-type material.  This material is positive
because there is a slight shortage of electrons.  (Electrons are negative,
so their absence makes the material positive).  Adding a small quantity of
a group V element (with five outer electrons), such as phosphorus, creates
N-type material.  Other elements can also be used to form semiconductors.

                             ┌─────┬─────┐
                      (+) ───┤  P  │  N  ├─── (-)
                             └─────┴─────┘

The simplest semiconductor is formed by joining P-type material and N-type
material to form a P-N junction.  This class of semiconductors includes
diodes and rectifiers.  The P-N junction is characterized by the fact that
electrons can flow (forward) from the N-type material to the P-type
material easier than (in reverse) from the P-type material to the N-type
material.  There is a forward voltage required, called the threshold
voltage, for the electrons to flow from the N-type to the P-type material.
A typical threshold voltage for a silicon diode is approximately 0.6 Volts.
For electrons to flow in the opposite direction usually requires a much
higher voltage, (50 Volts or larger).

In reality, electrons travel from a negative source, containing an excess
of electrons, to a positive source, containing a shortage of electrons.  By
convention, electrical current is assumed to flow in the opposite
direction, from a positive source to a negative source.  This convention
was established long before the discovery of the electron.

When a diode is reversed biased, the current remains constant until the
voltage reaches the break down voltage.  At the break down voltage the
current increases rapidly until the diode over heats destroying the diode.
When the diode is forward biased, the current increases exponentially until
the voltage reaches the threshold voltage.  At the threshold voltage the
diode will over heat destroying the diode.  The equation used to calculate
the current in a P-N junction is as follows:

              I = Irev exp(K V)

where:
       I     is the calculated current when the diode is forward biased
       Irev  is the theoretical current when the diode is reversed biased
       exp() is the exponential function "e" raised to the power of K V
       K     is a constant approximately equal to 39 for silicon
       V     is the forward biased voltage

A simple method for estimating the resistance of a forward biased diode, is
to set the effective resistance of the diode in such a way to maintain a
constant voltage drop across the diode equivalent to the threshold voltage.
Eventually, the diode will overload and burn out if too much current passes
through it.

The symbol for a diode looks like a triangle pointing to a vertical line,
as crudely represented below.  Conventional electrical current flows in the
direction that the triangle points.

                             │\ │
                      (+) ───┤ >├─── (-)
                             │/ │

                             Diode

The DIODE1.DC and DIODE2.DC circuits illustrate the characteristics of a
diode.  When plotting DIODE2.DC, the resulting curve is characteristic for
the current increasing expedientially as the voltage across the diode
approaches the threshold voltage.

This brings us to the next class of semiconductors, called transistors.
The name Transistor is derived from "Transient Resistor."  There are two
types of transistors, NPN and PNP, which are constructed of three
semiconductor materials sandwiched together.  The middle layer is called
the "Base", and the outer two layers are called the "Emitter," and
"Collector."  The thicknesses of each layer are not equal.  The Collector
is the thickest layer, and the Base is the thinnest layer.

                            ┌───────┬─┬─────┐
               Collector ───┤   N   │P│  N  ├─── Emitter
                            └───────┴┬┴─────┘
                                    Base

                            ┌───────┬─┬─────┐
               Collector ───┤   P   │N│  P  ├─── Emitter
                            └───────┴┬┴─────┘
                                    Base

This class of transistor is called a "bipolar" transistor, because current
flows through the transistor using two different methods.  In N-type
material, current flows as electrons move through the material.  In P-type
material, current flows as "holes" move through the material.

The symbol for a bipolar transistor is a three prong icon as crudely
represented below.  The prong with an arrow head is always the Emitter and
it points in the direction the (conventional) current flows.  The Emitter
in an NPN transistor points away from the Base, and the Emitter in a PNP
transistor points toward the Base.

                │ / Collector                   │  / Emitter
                │/                              │ /
        Base ───┤\                      Base ───┤└
                │ \                             │\
                │  ┘ Emitter                    │ \ Collector

               NPN                             PNP

I will only discuss the NPN transistor.  The PNP transistor works
identically, except that the direction of the current is reversed.  The
Base-Emitter junction acts like a P-N junction diode, but with a slightly
higher threshold voltage of approximately 0.7 Volts.  When the Base-Emitter
junction is reversed biased (the Emitter voltage is larger than the Base
voltage), the transistor is considered to be "Off," and very little current
can flow through the transistor.  When the Base-Emitter junction is forward
biased (the Base voltage is larger than the Emitter voltage), the
resistance between the Collector and Emitter is a function of the current
flowing between the Base and Emitter.  The more current through the Base-
Emitter junction, the smaller the resistance, and hence the larger the
current flowing between the Collector and Emitter.  The ratio of current
flowing between the Collector and Emitter, and the current flowing between
the Base and Emitter, is called the current gain designated "Hfe," and is
typically of the order of 100.  Hence, bipolar transistors are current
amplifiers.  The difference between the different bipolar transistors is
primarily the amount of current they can handle before overloading.
Computer circuits are designed to be fast, not powerful.

The resistance between the Base and the Emitter (Rbe) is calculated using
the same method for calculating the resistance for a diode.  The resistance
between the Collector and the Emitter (Rce) is calculated as follows:

              Rce = Rbe/Hfe

where:
       Rce = calculated resistance between the Collector and the Emitter
       Rbe = effective resistance between the Base and the Emitter
       Hfe = current gain

The TRANNPN.DC and TRANPNP.DC sample circuits illustrate the
characteristics of bipolar transistors.

A special type of transistor designed for high power and high gain (Hfe) is
called a darlington.  It is essentially two bipolar transistors back to
back on the same piece of silicon.  It is characterized by a threshold
voltage that is typically twice that of a bipolar transistor and has an
effective current gain (Hfe) of the order of a 1000 instead of a 100.  The
TRANDNPN.DC and TRANDPNP.DC sample circuits illustrate the characteristics
of darlingtons.  Note: when a darlington is turned On, there is a minimum
voltage across the Collector and Emitter equivalent to the threshold
voltage of a transistor (0.7 Volts).

A typical transistor in a computer circuit can only handle about 10
milliamps (mA) of current.  A typical medium range transistor, like the
2N2222, can handle up to ½ Amp.  A typical power darlington, like the
TIP100, can handle up to 8 Amps.

                 Gate                                Gate
                  │                                   │
            ┌─────┴─────┐                       ┌─────┴─────┐
            │   metal   │                       │   metal   │
            ├───────────┤                       ├───────────┤
            │   glass   │                       │   glass   │
            ├───┬───┬───┤                       ├───┬───┬───┤
  Source ───┤ P │   │ P ├─── Drain    Source ───┤ N │   │ N ├─── Drain
            ├───┘ N └───┤                       ├───┘ P └───┤
            │           │                       │           │
            └─────┬─────┘                       └─────┬─────┘
                  │                                   │
              Substrate                           Substrate

              P-Channel                           N-Channel

The last type of transistor to discuss is called the Metal Oxide
Semiconductor (MOS).  It is a type of Field Effect Transistor (FET).  This
transistor is similar to a bipolar transistor (NPN or PNP) with the
addition of a metal "Gate" over the "Substrate."  The Gate is separated
from the Substrate by a thin insulator, usually SiO2 (glass).  The symbols
for these types of transistors are crudely represented below:

        Gate ──┐├─── Source                    │├─── Drain
               │ ──> Substrate                 │ <── Substrate
               │├─── Drain              Gate ──┘├─── Source

              PMOS                            NMOS

When a positive voltage of at least 2 Volts is applied between the Gate and
a P-type Substrate, the electrons in the Substrate are pulled toward the
Gate allowing current to flow between the two N-type material called the
"Source" and the "Drain."  This is called an N-channel MOS (NMOS)
transistor.  The larger the voltage, the less resistance between the Source
and the Drain.  The resistance is inversely proportional to the voltage
(less the 2 Volt threshold voltage) squared as illustrated in the following
equation:

                      K
                R = ──────
                    (V-2)²

where:  R = The calculated resistance between the Source and the Drain
        K = A constant, approximately 5000 Ohms/Volt²
        V = Voltage potential between the Gate and the Substrate.

A similar P-channel MOS (PMOS) transistor exists, but requires a negative
voltage between the Gate and the N-type Substrate for current to flow
between the P-type Source and Drain.  The TRANPMOS.DC and TRANNMOS.DC
sample circuits illustrate the characteristics of MOS type transistors.

Unlike bipolar transistors which are current amplifiers, MOSFETs are
voltage amplifiers.
LOGIC

Before we can discuss actual computer circuits, we must first discuss the
concept of logic.  There are only two logical values: "TRUE" and "FALSE."
There are three fundamental logical operators from which all other logical
operators can be derived.  They are "NOT," "AND," and "OR."   The NOT
operator works as follows:  If it is NOT TRUE, it must be FALSE.
Conversely, if it is NOT FALSE, it must be TRUE.

All of the inputs must be TRUE for the AND operator to be TRUE.  Any of the
inputs can be TRUE for the OR operator to be TRUE.  The following table
summarize these fundamental logical operators:


               ╔═══════════════╦═══════════════════════════╗
               ║     Input     ║          Output           ║
               ╟───────┬───────╫────────┬─────────┬────────╢
               ║   A   │   B   ║ NOT A  │ A AND B │ A OR B ║
               ╠═══════╪═══════╬════════╪═════════╪════════╣
               ║ FALSE │ FALSE ║ TRUE   │  FALSE  │  FALSE ║
               ║ FALSE │ TRUE  ║ TRUE   │  FALSE  │  TRUE  ║
               ║ TRUE  │ FALSE ║ FALSE  │  FALSE  │  TRUE  ║
               ║ TRUE  │ TRUE  ║ FALSE  │  TRUE   │  TRUE  ║
               ╚═══════╧═══════╩════════╧═════════╧════════╝

In addition to the fundamental logical operators, there are three
additional logical operators that are commonly used and can be derived from
the three fundamental operators.  They are "NAND," "NOR," and Exclusive OR
"XOR."  The NAND operators is the same as "NOT AND."  In other words, the
result of the AND operator is complemented by the NOT operator.   The
logical equation for the NAND operator is the following:

                A NAND B = NOT (A AND B)

Similarly, the NOR operator is the same as "NOT OR."  The logical equation
for the NOR operator is the following:

                A NOR B = NOT (A OR B)

The Exclusive OR is similar to the OR operator, except only one input is
allowed to be TRUE at a time for the answer to be TRUE.  In other words,
the answer is TRUE if one or the other input is TRUE, but not both.  The
logical equation for Exclusive OR (XOR) is the following:

                A XOR B = (A OR B) AND NOT (A AND B)
                                or
                A XOR B = (A OR B) AND (A NAND B)

The following table summarizes the NAND, NOR, and XOR logical operators:

             ╔═══════════════╦═══════════════════════════════╗
             ║     Input     ║             Output            ║
             ╟───────┬───────╫───────────┬─────────┬─────────╢
             ║   A   │   B   ║ A NAND B  │ A NOR B │ A XOR B ║
             ╠═══════╪═══════╬═══════════╪═════════╪═════════╣
             ║ FALSE │ FALSE ║   TRUE    │  TRUE   │  FALSE  ║
             ║ FALSE │ TRUE  ║   TRUE    │  FALSE  │  TRUE   ║
             ║ TRUE  │ FALSE ║   TRUE    │  FALSE  │  TRUE   ║
             ║ TRUE  │ TRUE  ║   FALSE   │  FALSE  │  FALSE  ║
             ╚═══════╧═══════╩═══════════╧═════════╧═════════╝
I will now discuss the DeMorgan's theorem.  This theorem states that if you
invert the input and output of the AND operator, you obtain the same
results as the OR operator.  Conversely, if you invert the input and output
of the OR operator, you obtain the same results as the AND operator.  In
addition, there are corollaries to this theorem.  The logical equations for
this theorem and its corollaries are listed below:

                 A AND B = NOT ( (NOT A) OR (NOT B) )
                 A AND B = (NOT A) NOR (NOT B)
                  A OR B = NOT ( (NOT A) AND (NOT B) )
                  A OR B = (NOT A) NAND (NOT B)
                A NAND B = (NOT A) OR (NOT B)
                 A NOR B = (NOT A) AND (NOT B)

The DeMorgan's theorem can be extremely useful when designing logic
circuits.

It is actually possible to derive the three fundamental logical operators,
NOT, AND, and OR using a single logical operator, and subsequently derive
all logical operators from this single logical operator.  (The original
computer designers only had one or two logical operator circuits to work
with).  This logical operator can be either a NAND or a NOR logical
operator.

The following logical equations illustrate this capability:

                   NOT A = A NAND A
                 A AND B = NOT (A NAND B)
                  A OR B = (NOT A) NAND (NOT B)
                 A NOR B = NOT ( (NOT A) NAND (NOT B) )
                 A XOR B = NOT ( ( (NOT A) NAND (NOT B) NAND (A NAND B) )

                   NOT A = A NOR A
                 A AND B = (NOT A) NOR (NOT B)
                  A OR B = NOT (A NOR B)
                A NAND B = NOT ( (NOT A) NAND (NOT B) )
                 A XOR B = (A NOR B) NOR ( (NOT A) NOR (NOT B) )

How does this discussion on logic help explain how digital computers work?
A digital computer is a "Binary" computer.  Binary computers deal with only
two states: TRUE or FALSE, 1 or 0, On or Off, Voltage or Ground.  Binary
computers do not use varying voltages to represent values, instead they use
simple On/Off circuits.  This means that binary computer circuits do not
require precision electrical components.

The decimal numbering system we are familiar with uses ten different digits
(0 through 9), and is referred to as base 10.  A binary computer represents
numbers using base 2, which only has two digits "0" and "1."  In base 10,
the least significant (right most) digit is multiplied by 1, the next digit
by 10, 100, 1000, etc.  In base 2, the least significant digit is
multiplied by 1, the next by 2, 4, 8, etc.  So the decimal number 9 can be
represented by the binary number 1001.  (A binary digit is called a bit.)

The Exclusive OR logical operator is the fundamental basis for a binary
adder.  Once you have the ability to add two numbers together, you can than
subtract two numbers by converting one number to its negative value and
adding it to the other number.  Negative numbers are represented by using a
method called "Twos Compliment."  This method represents a negative one by
the largest possible number (all binary ones).  Hence when you add positive
one and negative one you get zero (and carry out).  To convert a number to
its negative value you must invert each digit using the NOT logical
operator, and add one via carry in.  You can multiply two numbers by using
a series of shifts and additions similar to long hand multiplication.
Finally you can divide two numbers by using a series of shifts and
subtractions.

LOGIC GATES

We finally get to the good stuff.  It is time to start building circuits
that can perform the various logical operations discussed above.  Circuits
that perform logical operations are usually referred to as "Logic Gates."
We will start with the simplest circuit using diodes.

Using only diodes and resistors we can build the AND and OR logic gates.
The sample circuits DIODEAND.DC and DIODEOR.DC illustrate these logic
gates.  In these circuits the switches are the inputs, where 5 Volts
represents a TRUE value, and ground (0 Volts) represents a FALSE value.

The DIODEAO.DC depicts a circuit with two ANDs and one OR logical operator
that solve the following equation:

                E = (A AND B) OR (C AND D)

                where E is the output

This sample circuit illustrates some of the limitations to pure diode logic
gates.  The first limitation is that the output voltage is not regenerated
(reset to 0 or 5 Volts) after each logic gate, hence the TRUE output of the
AND gate can be as little as 2.8 Volts, instead of 5 Volts as illustrated
in the previous example.  The reduced voltage is due to the Resistor-Diode-
Resistor circuit between the input diodes and the output stage.  To make
matters worse, the TRUE output of the OR gate can be as little as 2.2
Volts.  The second limitation is that diode circuits cannot function as a
logical NOT operator.

If we look back to the sample circuit of the NPN transistor (TRANNPN.DC),
we see that a single transistor can perform the function of the logical NOT
operator.  When the input is 5 Volts the output is 0 Volts, and vice versa.

DTL

By combining the Diode AND circuit for input and the Transistor NOT circuit
for output, we form the Diode-Transistor Logic (DTL) NAND gate, as depicted
in the sample circuit DTLNAND.DC.  It was necessary to add a diode between
the Diode AND circuit and the transistor because the threshold voltage of
the transistor and the diode is almost the same.  This diode protects
against false triggering of the transistor.  This circuit has the advantage
that the output voltage of each gate is always regenerated, so there is no
limit to how many gates can be connected in series.
By removing one of the input diodes, the NAND gate now functions as a NOT
gate (or Inverter).  The DTLNOT.DC sample circuit illustrates the NOT gate.
The PLTDTL.DC sample circuit allows you to vary the input voltage to see
how this circuit responds.  If you use the "p" command, you can plot the
voltage at each node as the input voltage varies from 0 Volts to 5 Volts.
When the input is approximately 0.5 Volts, the output of the logic gate
will change.

The logic AND gate can be formed by combining the NAND gate with the NOT
gate.  It is not necessary to use diodes in the internal NOT gate, when a
single transistor will suffice.  The sample circuit DTLAND.DC illustrates
this circuit.

The DTL OR gate does not use the Diode OR gate as an input stage.  If a
Diode OR was used, current would be allowed to flow through the input stage
into the remainder of the circuit.  The DTL NAND gate isolates the input
current from the remainder of the circuit.  To provide the same isolation
for the DTL OR gate, the OR gate is created using three NOT gates and an
AND gate as defined by DeMorgan's theorem:

                A OR B = NOT ( (NOT A) AND (NOT B) )

Two DTL NOT gates are used as an input stage, and the transistors'
Collectors and Emitters are tied together to form an AND gate.  A third DTL
NOT gate (a single transistor) is used for the output stage.  The final NOT
gate is required to provide a consistent output voltage independent of
whether one or both inputs are in the On position.  The sample circuit
DTLOR.DC illustrates this circuit.

By adding another NOT gate to the output stage of the OR gate, we form the
DTL NOR gate as illustrated in the DTLNOR.DC sample circuit.

Finally, the Exclusive OR (XOR) gate is illustrated in the DTLXOR.DC sample
circuit, and uses the DTL AND, OR, and NAND gates to solve the Exclusive OR
equation discussed earlier.  The traditional icons for the AND, OR, and
NAND gates are used in this program.  If you press the F1 key twice, a full
screen help message will appear identifying the icons used for logical
gates.

TTL

This brings us to the next family of logic gates called Transistor-
Transistor Logic (TTL).  The original TTL logic circuits used a multiple
Emitter transistor for input, and a pair of transistors arranged one above
the other for output.  The upper transistor is only On when the output is
TRUE, and the lower transistor is only On when the output is FALSE.   This
output configuration of transistors is referred to as the "Totem-Pole"
output.  The multiple Emitter transistor, which could only be manufactured
in an Integrated Circuit (IC) chip, performs the same basic function as the
Diode AND gate used in the DTL NAND gate.  Today's TTL circuits actually
use diodes for their input stage, just like the DTL circuits.  For this
reason, the sample TTL circuits in this program use diodes for input,
instead of the multiple Emitter transistor.  However, the rest of the TTL
circuit is characteristic of the original TTL circuits.

The sample circuits TTLNOT.DC, TTLNAND.DC, and TTLAND.DC depict the TTL
NOT, NAND and AND logic gates.  Notice that the TRUE output is not 5 Volts,
but 4 Volts.  The PLTTTL.DC sample circuit is configured with a
potentiometer for input and the voltage at each node can be plotted using
the "p" option.
The sample circuits TTLOR.DC and TTLNOR.DC illustrate the TTL OR and NOR
gates.  The input stage of these circuits are similar to the corresponding
DTL input stages, and the output stage contains the standard TTL totem-pole
output.

The Exclusive OR (XOR) gate is illustrated in the TTLXOR.DC sample circuit,
and uses the TTL AND, OR, and NAND gates to solve the Exclusive OR equation
discussed earlier.

In addition to the standard logic gates, TTL circuits offer a three state
gate that can turn Off both transistors in the totem-pole output stage.
Three state gates are typically used when the output of many gates are
connected together on a bus, and only one gate is permitted to be active at
a time.  The TTL3NOT.DC sample circuit is an example of a TTL three state
gate.  The top switch is connected to the data input.  Only when the bottom
switch is Off, will the output be enabled.

In general, TTL circuits are faster than DTL circuits.  Over the years
several variations of TTL circuits have evolved.  These variations include
Low-power (L), Schottky (S), Low-power Schottky (LS), and Advanced Low-
power Schottky (ALS or F) circuits.  Of these variations, the LS series is
the most commonly available since it is faster, cheaper, and requires less
power than the original TTL circuits.

                             ┌─────┬─────┐
                      (+) ───┤metal│  N  ├─── (-)
                             └─────┴─────┘

A "Schottky Diode" is a surface barrier diode composed of a metal (such as
gold) and  N-type material.  This diode is faster than a silicon diode and
has a threshold voltage about 0.3 Volts or half the threshold voltage of a
silicon diode.  The SKDIODE.DC sample circuit illustrates the operating
characteristics of a Schottky Diode.  The Schottky Diode symbol is crudely
depicted below:
                                ┌┐
                             │\ │
                      (+) ───┤ >├─── (-)
                             │/ │
                               └┘
                        Schottky Diode

The Low-power Schottky (LS) series logic gates employs Schottky Diodes
between the Base and Collector junction of each transistor preventing the
transistor from fully saturating (fully turned On).  By not fully
saturating the transistor, it can switch from On to Off much faster.  These
transistors are referred to as "Schottky Transistors" and are crudely
depicted below:

                ┌┐                              ┌┐
                │ / Collector                   │  / Emitter
                │/                              │ /
        Base ───┤\                      Base ───┤└
                │ \                             │\
                │  ┘ Emitter                    │ \ Collector
               └┘                              └┘

               NPN                             PNP
The SCHOTTKY.DC sample circuit illustrates operating characteristics of the
Schottky transistor.  The input stage of the LS series gates use Schottky
diodes instead of conventional diodes or multiple Emitter transistors.  The
LS series also uses Schottky diodes for negative input voltage protection.
The LSNOT.DC sample circuit depicts a typical LS series NOT gate.  The
PLTLS.DC sample circuit is configured with a potentiometer for input and
the voltage at each node can be plotted using the "p" option.

The sample circuits LSNAND.DC and LSAND.DC depict the LS NAND and AND logic
gates.  Note that when an LS gate output is TRUE the output voltage is
approximately 4 Volts.  When an LS gate output is FALSE the output voltage
is approximately 0.3 Volts.

The sample circuits LSOR.DC and LSNOR.DC illustrate the LS OR and NOR
gates.  The LS XOR circuit is similar to the DTL and TTL XOR circuit,
except it uses LS gates.

In addition to the standard logic gates, LS circuits offer a three state
gate that can turn Off both transistors in the totem-pole output stage.
Three state gates are typically used when the output of many gates are
connected together on a bus, and only one gate is permitted to be active at
a time.  The LS3NOT.DC sample circuit is an example of a LS three state
gate.  The bottom switch is connected to the data input.  Only when the top
switch is On, will the output be enabled.  Note: the output may oscillate
in this program when the output is disabled.

ECL

The last family of logic gates that use bipolar transistors is called
Emitter-Coupled Logic (ECL).  ECL gates maintain a partial current in each
transistor preventing them from saturating or turning Off.  This makes ECL
gates the fastest logic gates on the market.  Also, the difference in
voltage between TRUE and FALSE, is approximately 1 Volt.  The typical ECL
circuit consists of a differential amplifier input stage, a bias circuit,
and an Emitter-follower output.  Traditional ECL circuits operate using
ground and -5.2 Volts for power supply.  However, they can operate at 5
Volts and ground like other logic gates.  All the sample circuits in this
program use the 5 Volts and ground power supply for ECL logic gates.

The basic ECL gate is an OR-NOR gate, which is characterized by a dual
complementary output.  The ECLORNOR.DC sample circuit illustrates this
logic gate.  You may notice that an input device labeled "ECL" is inserted
between the switch and the circuit input.  This device consists of three
resistors and is required to convert 5 Volts and ground from a switch to
input voltages that are compatible with ECL circuits.  If this circuit was
not installed, the ECL node voltages would not be characteristic of ECL
circuits.

The ECLNOT.DC sample circuit illustrates the simplest of the ECL circuits,
with a single input and the traditional dual complementary outputs.  The
PLTECL.DC sample circuit, is the same NOT gate, but with a potentiometer
for input to illustrate the effects of varying the input voltage, on the
output voltage.

The ECL AND-NAND gate is derived using the OR-NOR gate as described by
DeMorgan's theorem:

                 A AND B = (NOT A) NOR (NOT B)
                A NAND B = (NOT A) OR (NOT B)

The ECLNAND.DC sample circuit illustrates the ECL AND-NAND gate.  Both
input stages start with a switch, followed by a switch-to-ECL converter,
followed by an ECL NOT gate.  The outputs of the OR-NOR gate must be
reversed, since the NOR output (top) becomes the AND output, and the OR
output (bottom) becomes the NAND output.

The ECL Exclusive OR gate also has dual complementary outputs and is
constructed using only NOT and OR-NOR gates.  You must reverse the OR-NOR
gate outputs, since OR becomes NXOR, and NOR becomes XOR.  The sample
circuit ECLXOR.DC illustrates this circuit which can also be represented by
the logical equation:

                A XOR B = (A NOR B) NOR ( (NOT A) OR (NOT B) )

Note: the ECLXOR.DC sample circuit uses 100 components.  This is the most
complex sample problem provided and will take the longest amount of time to
evaluate.

ECL gates are the fastest logic gates on the market, but they also require
the most power.  Hence, it is difficult to pack a lot of ECL gates on a
single integrated circuit chip without overheating the chip.

CMOS

The last family of logic gates I will discuss are called Complementary
Metal Oxide Semiconductors (CMOS).  The term complementary refers to the
use of two types of transistors in the output circuit in a configuration
similar to the totem-pole output in TTL.  The PMOS transistor is on top,
and the NMOS transistor is on the bottom.  The CMOSNOT.DC sample circuit
illustrates the NOT gate, which is the simplest of the CMOS gates.  The
PLTCMOS.DC sample circuits illustrates the effects of varying input voltage
on this gate.

The CMOS NAND gate consists of four transistors, two PMOS transistors in
parallel, and two NMOS transistors in series, as illustrated by the
CMOSNAND.DC sample circuit.  Both NMOS transistors must be On for the
output to be FALSE (0 Volts).  The CMOS AND gate is the same circuit
followed by a CMOS NOT gate as illustrated in the CMOSAND.DC sample
circuit.

The CMOS NOR gate also consists of four transistors, however the two PMOS
transistors are in series, and the two NMOS transistors are in parallel, as
illustrated CMOSNOR.DC sample circuit.  Both PMOS transistors must be On
for the output to be TRUE (5 Volts).  The CMOS OR gate is the same circuit
followed by a CMOS NOT gate as illustrated in the CMOSOR.DC sample circuit.

The CMOS Exclusive OR gate is similar to the DTL and TTL Exclusive OR
gates, except it uses CMOS AND, NAND, and OR gates as illustrated in the
CMOSXOR.DC sample circuit.

CMOS circuits can operate using a wide variety of power supply voltages.
Since the threshold voltage for the PMOS and NMOS transistors is 2 Volts,
the minimum power supply that CMOS circuits can use is approximately 3
Volts.  On the other hand, the power supply can be as large as 15 Volts.
This makes battery driven circuits very practical, since the circuits will
continue to operate as the battery gradually runs down.
CMOS gates are characterized by requiring very little power because the MOS
transistors use voltage to trigger, instead of current.  The same reason
that explains their low power consumption, also explains why CMOS gates are
the slowest logic gates (when the transistors are physically the same size
as the bipolar transistors in the previous logic families).  The speed of a
circuit is limited by the size and spacing of the components, and the speed
of light.  The speed of the electrons flowing through a circuit approaches
the speed of light, which is the theoretical speed limit.  However, today's
CMOS technology use very small transistors, with very thin insulators
between the Gate and Substrate of the transistor, and the Gates are now
made out of semiconductor material instead of aluminum metal.  Therefore
today's CMOS logic gates can be fast.  Because of their low power
consumption, they can be more densely packed on an integrated circuit chip.
As an example, the Intel 486 processor is based on CMOS technology,
contains more than a million transistors on a single chip, and can operate
at speeds up to 66 MHz (million cycles/second).  The Intel Pentium
processor contains more than 3 million transistors and can operate at 3.3
Volts with speeds up to 100 MHz.

INTEGRATED CIRCUITS (IC)

After the invention of semiconductors, the next major invention was the
Integrated Circuit (IC) chip, which places multiple semiconductor
components on a single semiconductor wafer.  An entire circuit constructed
of resistors, capacitors, diodes, and transistors can be etched on to a
single chip.  All the components are made from semiconductor P-type and
N-type material, and are connected together with a metal conductor, like
aluminum.  The resistor can be made of either P-type or N-type material.
By varying the thickness of this material and by winding it back and forth
in a small area, different resistance values can be achieved.  Diodes are
formed by the junction of P-type and N-type material.  Schottky diodes are
formed by the junction of a metal like gold with N-type material.
Capacitors are typically reverse biased diodes, which are characterized by
small reverse biased voltages.  NPN bipolar transistors are constructed by
embedding N-type material for both the Emitter and the Collector into a P-
type Base.  (To make PNP transistors, replace N-type with P-type and vice
versa).  CMOS transistors are similar to bipolar transistors, except there
is a metal or semiconductor (P-type or N-type) Gate over the Base of the
transistor separated by a thin insulator of SiO2 (glass).

The original ICs only contained a few components, possibly a single logic
gate.  As the technology improved, the components became smaller, and more
gates were placed on a single chip.  Eventually the ability to dissipate
the heat became the limiting factor.  Using today's CMOS technology, over a
million transistors can be placed on a single IC chip.

In the DC Circuit Analysis program, the term "Integrated Circuit" (IC)
takes on a slightly different meaning.  The DC Circuit Analysis library
contains both basic components (like resistors, diodes, and transistors)
and Integrated Circuits (like DTL NOT, TTL NAND, and CMOS NOR gates), which
are circuits created using the DC Circuit Analysis program, saved in a file
with a "DCL" extension, and referenced in the library.  The DC.DCL file
contains all the parameters and screen locations for each item in the
library.  (See the section below that describes this file format).  Each IC
is stored in a separate file.  As an example, the DTL NOT gate is stored in
the file DTLNOT.DCL located in the DCL sub-directory.  You can view this
circuit using the following command:

                DC DCL\DTLNOT.DCL R

You will notice that there is no power supply, no switches for input, and
all the nodes are set to 0 Volts.  The first nodes created correspond to
the connection points.  By convention, the connections are in the following
order: power supply, ground, inputs, and outputs.  DCL files are not always
easy to read, since they use the fewest number of nodes necessary for the
library.  Nodes can be moved around on the screen, but if you delete one of
the connection nodes, you cannot simply recreate it.  Since the order in
which the nodes were created is essential to maintain compatibility with
the DC.DCL file.  Please do not modify the DCL library files.

USER DEFINED ICs

Why did I discuss DCL files?  Because you can create your own circuits and
add them to the library.  The last eight icons in the library are reserved
for your use.  They are stored in the files DCL\U1.DCL through DCL\U8.DCL.
The connection nodes are already created and organized on the screen in a
pattern matching the icon connection points.  All you have to do is add
your circuits to these files.  You can embed other Ics into your circuit,
the only limitation is the 100 total components which includes the
components within each IC and the IC icon itself.  You can move the nodes
around the screen, but please do not delete them.  If you make a mistake in
your user defined IC file, you can start all over by copying the
DCL\USER.DCL file into the file you were working on.  This file provides a
good starting point.  Please do not modify the DCL\USER.DCL file.

MISCELLANEOUS EXAMPLES

Let's look at some miscellaneous examples.  Since my primary intention of
writing this program was to introduce you to computer circuits, I will
discuss some common computer circuits.  Due to the limitation of 100
components and the computer overhead to analyze complex circuits, I can
only discuss a few simple circuits.  To reduce the time required to analyze
these circuits, only CMOS technology will be used for these sample
circuits.

How does computer memory work?  The basis for all computer memory is the
Set-Reset (S-R) Latch, which consists of two NAND gates that are cross
connected.  The SRLATCH.DC sample circuit illustrates the S-R Latch.  This
circuit has two inputs and two outputs.  The output of the top NAND gate is
the normal output, and the output of the bottom NAND gate is the
complemented output.  The top switch Sets the latch to TRUE, when it is in
the Off position.  The bottom switch Resets the latch to FALSE, when it is
in the Off position.  When both switches are in the On position, the
circuit "remembers" what it was last set to.  However, the initial output
of this circuit is unknown and will oscillate in this program until it is
either Set or Reset using one of the switches.  Both switches should not be
in the Off position, since both outputs (which are suppose to be opposites
of each other) will both become TRUE.

The Data Latch is an improvement on the Set-Reset Latch.  The DLATCH.DC
sample circuit illustrates the Data Latch.  This circuits consists of four
NAND gates, where the two NAND gates on the right form the familiar Set-
Reset Latch described above.  The top switch is the data input, and the
bottom switch is the enable input.  When the bottom switch is On, the input
data is stored in the latch.  When the bottom switch is Off, the input data
is ignored, and the circuit remembers its last setting.

The Data Flip-Flop is an example of a Master-Slave Flip-Flop.  It consists
of two latches connected in series and is illustrated in the FLIPFLOP.DC
sample circuit.  The first (Master) latch is a standard Data Latch as
described above.  The second (Slave) latch is a Set-Reset Latch with
enable.  When the enable input is On, the value of the Data input is stored
in the first latch.  When the enable input is Off, the value stored in the
first latch is transferred to the second latch.  Applications for Flip-
Flops include binary counters.  Initially, the output of the Flip-Flop is
unknown an will oscillate in this program until the lower switch changes.

The next set of circuits I will discuss are adders.  I will start with the
Half-Adder.  This circuits adds two binary numbers together and has two
outputs: Sum and Carry.  The Half-Adder is a variation on the Exclusive OR
circuit.  The HALFADDR.DC sample circuit illustrates the Half-Adder, as
described by the following logical equations:

                  Sum = A XOR B
                Carry = A AND B

The truth table for a Half-Adder is as follows:

                          ╔═══════╦════════════╗
                          ║ Input ║   Output   ║
                          ╟───┬───╫─────┬──────╢
                          ║ A │ B ║ Sum │ Carry║
                          ╠═══╪═══╬═════╪══════╣
                          ║ 0 │ 0 ║  0  │   0  ║
                          ║ 0 │ 1 ║  1  │   0  ║
                          ║ 1 │ 0 ║  1  │   0  ║
                          ║ 1 │ 1 ║  0  │   1  ║
                          ╚═══╧═══╩═════╧══════╝

The Full-Adder is essentially two Half-Adders in series.  The Full-Adder
has three inputs: A, B, and Carry (C) from the previous least significant
digit.  It also has two outputs: Sum and Carry.  Full-Adders can be
connected in series to handle larger numbers.  The FULLADDR.DC sample
circuit illustrates a Full-Adder, as described by the following logical
equations:

                  Sum = (A XOR B) XOR C
                Carry = (A AND B) OR (A AND C) OR (B AND C)

The truth table for a Full-Adder is as follows:

                        ╔═══════════╦════════════╗
                        ║   Input   ║   Output   ║
                        ╟───┬───┬───╫─────┬──────╢
                        ║ A │ B │ C ║ Sum │ Carry║
                        ╠═══╪═══╪═══╬═════╪══════╣
                        ║ 0 │ 0 │ 0 ║  0  │   0  ║
                        ║ 0 │ 0 │ 1 ║  1  │   0  ║
                        ║ 0 │ 1 │ 0 ║  1  │   0  ║
                        ║ 0 │ 1 │ 1 ║  0  │   1  ║
                        ║ 1 │ 0 │ 0 ║  1  │   0  ║
                        ║ 1 │ 0 │ 1 ║  0  │   1  ║
                        ║ 1 │ 1 │ 0 ║  0  │   1  ║
                        ║ 1 │ 1 │ 1 ║  1  │   1  ║
                        ╚═══╧═══╧═══╩═════╧══════╝

Due to limitations of this program, it is not practical to attempt to show
more complex logic circuits.  If you would like to learn more about
computer logic circuits, I recommend you invest in the "Logic Circuit
Analysis" program that I wrote.  It is cable of handling 1,000 logic gates,
which is enough to model an entire 4-bit Central Processing Unit (CPU).

Sometimes it is necessary to interface computer circuits to the outside
world.  The first circuit I will discuss is a Digital to Analog (D/A)
converter.  The simplest D/A consists of a resistor circuit.  The DTOA.DC
sample circuit is an example of a D/A.  The top switch is the most
significant digit and the bottom switch is the least significant digit.  If
you turn Off all the switches, and then turn only one switch On at a time,
you will notice that the top switch adds 2.5 Volts (½ the power supply
voltage), the second switch adds 1.25 Volts (¼ the power supply voltage),
the third switch 0.625 Volts, and the last switch 0.3125 Volts (or 1/16 the
power supply voltage).  This circuit can easily be interfaced with CMOS
logic gates, but not with the other family of logic gates.  That is because
CMOS logic is the only logic family with full 0 to 5 Volt output.

The next circuit is a CMOS Analog Switch.  The ANALOGSW.DC sample circuit
illustrates this circuit.  It uses a CMOS NOT circuit and a pair of MOS
transistors.  However, they are configured such that the switch can turn
both transistors On, or both Off.  When they are both On, they will provide
a small resistance allowing current to flow in either direction.  A typical
use of analog switches is to multiplex multiple analog signals into a
single Analog to Digital converter.

This brings us to Solid State Switches.  Sometimes it is necessary for a
digital circuit to control an electrical device, such as a light bulb, or a
motor.  The SSSW.DC and SSPOWSW.DC sample circuits illustrate solid state
switches capable of switching loads up to ½ Amp and 8 Amps respectively.
The first circuit uses a 2N2222 transistor to switch up to a ½ Amp load,
and the second circuit adds a TIP100 power darlington to switch up to an 8
Amp load.  The 100 ohm resistor represents the load in both cases.  Higher
voltages can be controlled, but the resistor values must be changed and you
will have to use larger Wattage resistors.  (All resistors in this library
are only rated at ¼ Watts).

The final sample circuit, SSRPOWSW.DC is a Solid State Reversible Power
Switch which uses four power transistors (two NPN and two PNP) for its
output.  This circuit can turn the load On and Off, as well as reverse the
power applied to the load.  The top switch is the On/Off switch, and the
bottom switch is the Forward/Reverse switch.  In this circuit each TTL AND
gate controls one 2N2222 transistor. The 2N2222 transistor controls both
the PNP power transistor and the NPN power transistor located in the
opposite corners.  The TTL logic assures that all four power transistors
are not turned On at the same time, but can all be turned Off.  The reverse
biased diodes are required to protect the power transistors when this
circuit is used to control a motor.  In addition, you should add a
capacitor across the motor.

I hope you enjoyed this tutorial and will continue to use this program to
explore other Direct Current (DC) circuits.  This program allows you to try
some circuits without actually building the circuit.

SPECIFICATIONS

        REQUIREMENTS
        ────────────
        IBM-PC or compatible computer with a 286 or later processor
        800 KB of disk space
        300 KB minimum available RAM, (after DOS, drivers and TSR)
        350 KB maximum available RAM required when there is no EMS
        EGA or VGA graphics adapter with 256 KB of RAM installed
        Color Monitor

        SUPPORTS (but not required)
        ───────────────────────────
        Mouse (2 or 3 button) with MOUSE.SYS or MOUSE.COM device driver.
        If a Math coprocessor installed, the program will run faster.
        If 64 KB of Expanded Memory (EMS) is available, it will be used.

        DOS ENVIRONMENTAL VARIABLES
        ───────────────────────────
        TMP     Sets location of DC.PCX and DC.DC file, otherwise written
                to the default directory.
                Example: SET TMP=D:\

        MONITOR Can be set to EGA or VGA.  The program will automatically
                detect if an EGA or VGA adapter is installed.  The MONITOR
                variable will override the automatic detection.
                Example: SET MONITOR=EGA

        EMS     Can be set to OFF or NO to override auto-detection so not
                to use EMS memory even if it is available.
                Example: SET EMS=OFF

        DC_DV   Used to override the convergence criteria.  If it takes a
                long time to display calculation results, you may want to
                set this variable to 1.0e-8.  This may speed up the program
                but reduce the accuracy of the results.
                Example: SET DC_DV=1.0e-8

        DC_PLOT Used to override the potentiometer increments used during
                plotting.  This value may range from 1% to 5%.
                Example: SET DC_PLOT=5


        PROGRAM LIMITS
        ──────────────
        112 Library Entries
        100 Components per circuit, including ICs and their components
        250 Nodes per circuit
        750 Connections per circuit
          8 User Definable Circuits
          8 Connection terminals per IC
          5 Connections per node.

SUMMARY OF KEYS

        TUTORIAL SCREEN
                Cursor Keys - Highlight the desired keyword
                ENTER - Select the highlighted keyword
                PGDN - Display next screen
                PGUP - Display previous screen
                F1 - Display opening tutorial screen
                ESC - Exit tutorial

        OPENING MENU
                Cursor Keys - Highlight the desired item
                HOME - Highlight "Analyze Circuit"
                END - Highlight "Exit"
                F5 - Display tutorial
                ENTER - Select the highlighted item

        SELECT SAMPLE CIRCUIT MENU
                PGUP, PGDN - Display additional pages of sample circuits
                Cursor Keys - Highlight the desired sample circuit
                HOME - Highlight the first sample circuit on this page
                END - Highlight the last sample circuit on this page
                ENTER - Select the highlighted sample circuit
                ESC, F10 - Exit menu without selecting a sample circuit

        ANALYZE CIRCUIT
                LEFT and RIGHT - Highlight Adjustable Component
                                 (Switch or Potentiometer)
                Switch:
                        UP, PGUP, HOME - Set to up position
                        DOWN, PGDN, END - Set to down position
                        ENTER - Toggle Switch
                Potentiometer:
                        HOME - Set to 99%
                        ENTER, PGUP - Increment by 10%
                        UP - Increment by 1%
                        DOWN - Decrement by 1%
                        PGDN - Decrement by 10%
                        END - Set to 1%
                F5 - Display tutorial
                F6 - Edit circuit
                p - Plot node voltage vs. potentiometer voltage
                w - Save screen into PC Paintbrush compatible file
                F10, ESC - Exit

        MODIFY CIRCUIT
                F1 - Help (Second F1 for full screen help)
                F2 - Redraw screen
                F3 - Move a Component (Node or IC)
                F4 - Access Library of Components
                F5 - Display tutorial
                F6 - Analyze circuit
                Cursor Keys - Move Cursor
                CTRL-BACKSPACE - Delete Component (Node or IC)
                ENTER - Make a Connection, or Lock Component in position
                F10, ESC - Exit

        LIBRARY OF COMPONENTS
                F1 - Help (Second F1 for full screen help)
                Cursor Keys - Highlight Component (Node or IC)
                PGUP, PGDN - Switch Pages of Library Components
                ENTER - Select Component
                F10, ESC - Exit

LIBRARY

The Library is based on the following components:
Resistors are standard values, ¼ Watts, 5% carbon resistors
Potentiometers are linear and are rated at 2 Watts
Silicon Diodes are 1N914 high speed switching Diodes (10 mA)
Schottky Diodes can carry up to 20 mA
NPN Transistors are 2N2222 500 mA, with Hfe = 150
PNP Transistors are 2N2904 500 mA, with Hfe = 150
NPN Darlingtons are TIP100 8 Amp, with Hfe = 2000
PNP Darlingtons are TIP105 8 Amp, with Hfe = 3000
PMOS and NMOS transistors are standard CMOS transistors
ICs are circuits created using the DC Circuit Analysis program and made
available in the library.

The Library contains the following items:

Type                    Description
─────   ───────────────────────────────────────────────
INODE   Interconnect Node
VNODE   Fixed Voltage Node,   0 Volts (Ground)
VNODE   Fixed Voltage Node,   5 Volts
VNODE   Fixed Voltage Node,  -5 Volts
VNODE   Fixed Voltage Node,  10 Volts
VNODE   Fixed Voltage Node, -10 Volts
SNODE   Switch Node,          5 Volts and   0 Volts (Ground)
SNODE   Switch Node,         10 Volts and -10 Volts

R       Resistor,           100 Ohms, ¼ Watts
R       Resistor,           130 Ohms, ¼ Watts
R       Resistor,           240 Ohms, ¼ Watts
R       Resistor,           470 Ohms, ¼ Watts
R       Resistor,           750 Ohms, ¼ Watts
R       Resistor,         1,000 Ohms, ¼ Watts
R       Resistor,         1,600 Ohms, ¼ Watts
R       Resistor,         2,000 Ohms, ¼ Watts

R       Resistor,         3,000 Ohms, ¼ Watts
R       Resistor,         3,900 Ohms, ¼ Watts
R       Resistor,         4,700 Ohms, ¼ Watts
R       Resistor,            10 Kilohms, ¼ Watts
R       Resistor,            20 Kilohms, ¼ Watts
R       Resistor,            47 Kilohms, ¼ Watts
R       Resistor,           100 Kilohms, ¼ Watts
R       Resistor,         1,000 Kilohms, ¼ Watts

R       Resistor,           100 Ohms, ¼ Watts
R       Resistor,           130 Ohms, ¼ Watts
R       Resistor,           240 Ohms, ¼ Watts
R       Resistor,           470 Ohms, ¼ Watts
R       Resistor,           750 Ohms, ¼ Watts
R       Resistor,         1,000 Ohms, ¼ Watts
R       Resistor,         1,600 Ohms, ¼ Watts
R       Resistor,         2,000 Ohms, ¼ Watts

R       Resistor,         3,000 Ohms, ¼ Watts
R       Resistor,         3,900 Ohms, ¼ Watts
R       Resistor,         4,700 Ohms, ¼ Watts
R       Resistor,            10 Kilohms, ¼ Watts
R       Resistor,            20 Kilohms, ¼ Watts
R       Resistor,            47 Kilohms, ¼ Watts
R       Resistor,           100 Kilohms, ¼ Watts
R       Resistor,         1,000 Kilohms, ¼ Watts

POT     Potentiometer,       1 Kilohms, 2 Watts
POT     Potentiometer,      10 Kilohms, 2 Watts
DIODE   Switching Diode,  1N914 10 milliamps
DIODE   Switching Diode,  1N914 10 milliamps
DIODE   Switching Diode,  1N914 10 milliamps
DIODE   Switching Diode,  1N914 10 milliamps
PMOS    PMOS Transistor,  (CMOS) 10 milliamps
NMOS    NMOS Transistor,  (CMOS) 10 milliamps

NPN     NPN Transistor,   2N2222 500 milliamps, Hfe=150
NPN     NPN Transistor,   2N2222 500 milliamps, Hfe=150
PNP     PNP Transistor,   2N2904 500 milliamps, Hfe=150
PNP     PNP Transistor,   2N2904 500 milliamps, Hfe=150
IC      Integrated Circuit,    DNPNL.DCL,    NPN Darlington
IC      Integrated Circuit,    DNPNR.DCL,    NPN Darlington
IC      Integrated Circuit,    DPNPL.DCL,    PNP Darlington
IC      Integrated Circuit,    DPNPR.DCL,    PNP Darlington

IC      Integrated Circuit,    DTLNOT.DCL,   DTL Inverter (NOT)
IC      Integrated Circuit,    TTLNOT.DCL,   TTL Inverter (NOT)
IC      Integrated Circuit,    CMOSNOT.DCL,  CMOS Inverter (NOT)
IC      Integrated Circuit,    ECLNOT.DCL,   ECL Differential output
IC      Integrated Circuit,    ECL116.DCL,   ECL Differential input &
output
IC      Integrated Circuit,    ECLOR.DCL,    ECL 2-In OR/NOR
IC      Integrated Circuit,    ECLOR3.DCL,   ECL 3-In OR/NOR
IC      Integrated Circuit,    ECLAND.DCL,   ECL 2-In AND/NAND

IC      Integrated Circuit,    DTLAND.DCL,   DTL 2-In AND
IC      Integrated Circuit,    DTLAND3.DCL,  DTL 3-In AND
IC      Integrated Circuit,    DTLOR.DCL,    DTL 2-In OR
IC      Integrated Circuit,    DTLOR3.DCL,   DTL 3-In OR
IC      Integrated Circuit,    DTLNAND.DCL,  DTL 2-In NAND
IC      Integrated Circuit,    DTLNAND3.DCL, DTL 3-In NAND
IC      Integrated Circuit,    DTLNOR.DCL,   DTL 2-In NOR
IC      Integrated Circuit,    DTLNOR3.DCL,  DTL 3-In NOR

IC      Integrated Circuit,    TTLAND.DCL,   TTL 2-In AND
IC      Integrated Circuit,    TTLAND3.DCL,  TTL 3-In AND
IC      Integrated Circuit,    TTLOR.DCL,    TTL 2-In OR
IC      Integrated Circuit,    TTLOR3.DCL,   TTL 3-In OR
IC      Integrated Circuit,    TTLNAND.DCL,  TTL 2-In NAND
IC      Integrated Circuit,    TTLNAND3.DCL, TTL 3-In NAND
IC      Integrated Circuit,    TTLNOR.DCL,   TTL 2-In OR
IC      Integrated Circuit,    TTLNOR3.DCL,  TTL 3-In NOR

IC      Integrated Circuit,    CMOSAND.DCL,  CMOS 2-In AND
IC      Integrated Circuit,    CMOSAND3.DCL, CMOS 3-In AND
IC      Integrated Circuit,    CMOSOR.DCL,   CMOS 2-In OR
IC      Integrated Circuit,    CMOSOR3.DCL,  CMOS 3-In OR
IC      Integrated Circuit,    CMOSNAND.DCL, CMOS 2-In NAND
IC      Integrated Circuit,    CMOSNND3.DCL, CMOS 3-In NAND
IC      Integrated Circuit,    CMOSNOR.DCL,  CMOS 2-In NOR
IC      Integrated Circuit,    CMOSNOR3.DCL, CMOS 3-In NOR

IC      Integrated Circuit,    DTLXOR.DCL,   DTL Exclusive OR
IC      Integrated Circuit,    TTLXOR.DCL.   TTL Exclusive OR
IC      Integrated Circuit,    CMOSXOR.DCL,  CMOS Exclusive OR
IC      Integrated Circuit,    ECLXOR.DCL,   ECL Exclusive OR/NOR
IC      Integrated Circuit,    ECLIN.DCL,    Switch to ECL Input
IC      Integrated Circuit,    DTOA.DCL,     Digital to Analog Converter
IC      Integrated Circuit,    SCHOTTKY.DCL, NPN Schottky Transistor
IC      Integrated Circuit,    SCHOTTKR.DCL, NPN Schottky Transistor

Diode   20 mA Schottky Diode
Diode   20 mA Schottky Diode
Diode   20 mA Schottky Diode
Diode   20 mA Schottky Diode
IC      Integrated Circuit,    User.DCL,     Reserved
IC      Integrated Circuit,    User.DCL,     Reserved
IC      Integrated Circuit,    User.DCL,     Reserved
IC      Integrated Circuit,    User.DCL,     Reserved

IC      Integrated Circuit,    U1.DCL,       User Defined IC
IC      Integrated Circuit,    U2.DCL,       User Defined IC
IC      Integrated Circuit,    U3.DCL,       User Defined IC
IC      Integrated Circuit,    U4.DCL,       User Defined IC
IC      Integrated Circuit,    U5.DCL,       User Defined IC
IC      Integrated Circuit,    U6.DCL,       User Defined IC
IC      Integrated Circuit,    U7.DCL,       User Defined IC
IC      Integrated Circuit,    U8.DCL,       User Defined IC

SAMPLE CIRCUITS

The following examples can be found in the \DC13\DC sub-directory:

Filename                        Description
───────────     ───────────────────────────────────────────────
ANALOGSW.DC     CMOS Analog Switch
CMOSAND.DC      CMOS 2-In AND
CMOSNAND.DC     CMOS 2-In NAND
CMOSNOR.DC      CMOS 2-In NOR
CMOSNOT.DC      CMOS Inverter (NOT)
CMOSOR.DC       CMOS 2-In OR
CMOSXOR.DC      CMOS Exclusive OR
DIODE1.DC       Sample Diode Circuits
DIODE2.DC       Plot of Diode Circuit
DIODEAND.DC     2-In Diode AND
DIODEAO.DC      Two 2-In Diode AND, and One 2-In Diode OR
DIODEOR.DC      2-In Diode OR
DLATCH.DC       Data Latch
DTLAND.DC       DTL 2-In AND
DTLNAND.DC      DTL 2-In NAND
DTLNOR.DC       DTL 2-In NOR
DTLNOT.DC       DTL Inverter (NOT)
DTLOR.DC        DTL 2-In OR
DTLXOR.DC       DTL Exclusive OR
DTOA.DC         Digital to Analog Converter
ECLNAND.DC      ECL 2-In AND/NAND
ECLNOT.DC       ECL Driver with Differential Output
ECLORNOR.DC     ECL 2-In OR/NOR
ECLXOR.DC       ECL Exclusive OR
FLIPFLOP.DC     Data Flip-Flop
FULLADDR.DC     Full Adder
HALFADDR.DC     Half Adder
LS3NOT.DC       TTL Low-Power Schottky (LS) Three State Inverter
LSAND.DC        TTL Low-Power Schottky (LS) 2-In AND
LSNAND.DC       TTL Low-Power Schottky (LS) 2-In NAND
LSNOR.DC        TTL Low-Power Schottky (LS) 2-In NOR
LSNOT.DC        TTL Low-Power Schottky (LS) Inverter (NOT)
LSOR.DC         TTL Low-Power Schottky (LS) 2-In OR
PLTCMOS.DC      Plot of CMOS Inverter (NOT)
PLTDTL.DC       Plot of DTL Inverter (NOT)
PLTECL.DC       Plot of ECL Driver with Differential Output
PLTLS.DC        Plot of TTL Low-Power Schottky (LS) Inverter (NOT)
PLTTTL.DC       Plot of TTL Inverter (NOT)
RESIST1.DC      Sample Resistor Circuits
RESIST2.DC      Sample Potentiometer Circuit
RESIST3.DC      A very complex resistor network
SCHOTTKY.DC     NPN Schottky Transistor
SKDIODE.DC      Schottky Diode
SRLATCH.DC      Set-Reset Latch
SSPOWSW.DC      8 Amp Solid State Switch
SSRPOWSW.DC     8 Amp Reversible Solid State Switch
SSSW.DC         ½ Amp Solid State Switch
STEPPER.DC      Stepper Motor Driver Circuit
TRANDNPN.DC     NPN Darlington
TRANDPNP.DC     PNP Darlington
TRANNMOS.DC     NMOS Transistor
TRANNPN.DC      NPN Transistor
TRANPMOS.DC     PMOS Transistor
TRANPNP.DC      PNP Transistor
TTL3NOT.DC      TTL Three State Inverter
TTLAND.DC       TTL 2-In AND
TTLNAND.DC      TTL 2-In NAND
TTLNOR.DC       TTL 2-In NOR
TTLNOT.DC       TTL Inverter (NOT)
TTLOR.DC        TTL 2-In OR
TTLXOR.DC       TTL Exclusive OR

DC.DCL FILE FORMAT

DC.DCL contains the specifications for each library entry.  There is one
line for each entry as follows:

TYPE NL NC NP  --- Locations x y ---  --- Parameters ---

where TYPE is:
   INODE - Interconnection Node
   VNODE - Fixed Voltage Node
   SNODE - Switch Voltage Node
   R     - Resistor
   POT   - Potentiometer
   DIODE - DIODE
   PMOS  - P-channel CMOS transistor
   NMOS  - N-channel CMOS transistor
   NPN   - NPN bipolar transistor or darlington
   PNP   - PNP bipolar transistor or darlington
   IC    - Integrated Circuit - Stored in separate files

NL: Number of Locations
NC: Number of Connections must be less then or equal to NL
NP: Number of Parameters

--- Locations x y ---
Locations specified in x y pairs relative to upper left corner of icon.
The first NC locations are the connections, any additional locations are
for Resistor current, Potentiometer % turns, or INODE Voltage labels.

--- Parameters ---
The number and type of parameters depends on the TYPE as follows:

TYPE  NL NC NP           Locations                     Parameters
───── ── ── ──  ───────────────────────────   ───────────────────────────
INODE  2  1  0  connection, Voltage Label     none
VNODE  1  1  1  connection                    Fixed Voltage
SNODE  1  1  2  connection                    Up Voltage, Down Voltage
R      3  2  2  First, Second, Amp Label      Resistance, Rated Wattage
POT    4  3  2  Top, Bottom, Middle, % Label  Resistance, Rated Wattage
DIODE  2  2  3  Plus, Negative                Vth, Amp, HiZ Resistance
PMOS   4  4  4  Gate, Source, Base, Drain     Vth, Ohms/Volt², Amp, HiZ R
NMOS   4  4  4  Gate, Source, Base, Drain     Vth, Ohms/Volt², Amp, HiZ R
NPN    3  3  4  Emitter, Base, Collector      Vth, Hfe, Amp, HiZ R
PNP    3  3  4  Emitter, Base, Collector      Vth, Hfe, Amp, HiZ R
IC     ?  ? -1  +V, -V, Inputs, Outputs       dcl\filename.DCL
                Up to Eight Connections

Integrated Circuits (ICs) files are stored in the \DC13\DCL sub-directory.
ICs are all predefined DC Circuits that contain Components or other ICs.

DC AND DCL FILE FORMATS

Files with the extension "DC" are sample circuit files located in the DC
sub-directory.  Files with the extension "DCL" are library (IC) circuit
files located in the DCL sub-directory.  Both files contains circuit
created by the DC Circuit Analysis program, and have the same format:

The first line contains two numbers as follows:

NC NN
        where   NC = Number of Components or ICs
                NN = Number of Nodes (Interconnect, Fixed, or Switch)

The next NC lines contains the components, one per line as follows:

LIB ROW COL N N1 N2 ...
        where   LIB = Library entry (0-111)
                ROW = Screen row location of icon (0-299)
                COL = Screen column location of icon (0-79)
                N   = Number of connection terminals
                N1, N2, ... = Node corresponding to each connection
                        Nodes are numbered starting with 100

The next NN lines contains the nodes, one per line as follows:

LIB ROW COL N  C1 CC1  C2 CC2
        where   LIB = Library entry (0-111)
                ROW = Screen row location of icon (0-299)
                COL = Screen column location of icon (0-79)
                N   = Number of connections
                C1, C2, ... = Component (0-99), or Node
                CC1, CC2, ... = Connection on component or Node C1, C2, ...