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1988-02-13
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5KB
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127 lines
Active Filter Design V1.5
(c) 1988 L.P. Kahhan
This program is being placed on the market as SHAREWARE. It is not
free software. The user is granted a limited license to use this
product for a period of 30 days, at which time they are expected to
either register the software for continued use, or to stop using the
software and destroy all copies. This software may be freely
distributed, either via disk, or bulletin board systems, provided that
the program and documentation files are left intact and not modified
in any way. Registering this software will not only enable you to
obtain support and bug fixes, but will encourage the development of
new and more diverse engineering software packages. To register, send
a check or money in the amount of $15.00 order to:
Larry P. Kahhan
519 Fairman Lane
Langhorne, PA 19047
Quantity discounts and site licensing info. available on request.
WARRANTY
This software is provided without warranty, express or implied, of any
kind. Although reasonable care has been exercised in the preparation
and testing of this package, I can in no way be held responsible for
any damages arising out of any use or mis-use of this package. It is
up to the user to verify any designs produced by this package prior to
implementation.
PROGRAM FEATURES
In using this program, all entries must be entered as real numbers,
not in engineering units, e.g., if entering a filter's cutoff
frequency or center frequency, enter 2000, not 2K or 2 kHz. When asked
to select a capacitor value, the value is to be entered in micro-
farads, e.g. .01, not .01 uf.
This package allows the user to quickly determine values for a variety
of filter types as follows:
1. Low-pass
a. 2nd order Butterworth
b. 2nd order Chebychev
c. 4th order Butterworth
d. 4th order Chebychev
2. High-pass
a. 2nd order Butterworth
b. 2nd order Chebychev
c. 4th order Butterworth
d. 4th order Chebychev
3. Band-pass
a. For Q <= 10
b. For Q <= 40
4. Band-reject
For each filter type, select the desired implementation from the menu
and follow the on-screen instructions. As you work your way through
the menus, you'll see that only specific values of filter order, gain,
and Q are permitted. The program output is shown in schematic form on
the CRT, and may be printed on any dot matrix printer supporting IBM's
Pro-printer line graphics. Resistor values should be converted by the
user to the nearest standard 5%, 2%, or 1% value, as the values
calculated are pretty close to exact for the specified filter
parameters, and may not be commercially available values. Future
versions of this package may allow greater variety of selection of
filter parameters, as well as the ability to generate a netlist for
analysis by such commercially available packages such as ECA by TATUM
LABS.
PROGRAM SOURCE CODE
This is my first attempt at writing a shareware package, and was
quickly put together using QuickBasic 4.0, the new MicroSoft Basic
compiler. The source code will not be made publicly available, but
I'll consider making custom modifications to this package on a
consulting basis.
CHANGES FROM ORIGINAL RELEASE
The bugs found and corrected in the original release are as
follows:
1. Bandpass filters with a Q>= 40 will now work. The
original problem was due to a typographical error.
2. Resistor values were rounded up to the nearest integer
such that values of less than 1K were displayed as 0k.
This has been corrected, and an attempt has been made
to display at least 2 or 3 significant digits. Values
of less than 1K will be displayed as, e.g., .5K for
the value of 500 ohms. All values are still displayed
in K-ohms.
3. In checking through every path for one final test
before releasing V1.5, bugs were found in 3 filter
types affecting numerical accuracy. These filters were
the 2nd order high-pass Chebychev, 4th order
high-pass Chebychev, and multiple feedback bandpass
filter. These bugs have been corrected.
User feedback is welcome. If additional bugs are uncovered, please
bring them to my attention. They will be corrected in the next
release.