Dependent Current Source

Description

A Dependent Current Source is a source that supplies a current that depends on the value of one, or more voltages or currents, elsewhere in the circuit, multiplied by a coefficient. The dependency can be based on voltages or currents specified by Circuit Tags, or Independent Sources. Here is a small circuit with a Dependent Current Source labeled "ic".


The Dependent Current Source, "ic", is a current source that depends on other currents in the circuit, namely those specified by the tags 'i1', 'i2', and 'Iin'.

Parameters Dialog Box

The parameters of a Dependent current Source are edited with this dialog box.

Label

An alphanumeric label to provide a reference to the Dependent current Source.

Type of Dependency

These two radio buttons select a voltage or current dependency. A Dependent Current Source's dependency can be based on voltage tags and voltage sources, or it can be based on current tags and current sources.

Dependency List

This is a list of the labels of the circuit's existing Sources and Circuit Tags. The list will display voltage tags and voltage sources, or it will display current tags and current sources depending on the selected "Type of Dependency".

The list shows 'i1' (the current through the 60 Kohm Resistor in the circuit above), 'i2' (the current through the 40 Kohm Resistor), and 'Iin' (the current through the 50 ohm Resistor, which is equal to the current supplied by the source, 'Vin')

There is a '+' sign next to all three labels, which means that this Dependent Current Source's current is dependent on the summation of all three currents. Notice that the summation of all three currents is equal to the current flowing to the right through the source 'Vo'. Current Tags can only be placed across passive components. So, to express the current through the source 'Vo', it is necessary to sum the currents through one passive component in each of the other branches connected to the same node as 'Vo'.

If any label had a '-' sign next to it then the dependency summation would include the opposite of the positive current flow indicated by that label's Current Tag, or Current Source.

Click the left mouse button on any label in the Dependency List to rotate the sign of the label. The sign of the label can be blank, '+', or '-'.

• If the sign is blank, then the label does not contribute to the dependency of this source.
• If the sign is '+' or '-', then the signal represented by the label is added to, or subtracted from the dependency of the source.

Dependency Coefficient

The Dependency Coefficient is a rational number formed from two real numbers. The top number is divided by the bottom number to form the coefficient which is then multiplied by the summation of the dependencies.

Therefore, the current supplied by the Dependent Current Source, 'ic', in the circuit above, will be:

Label Position

The Dependent Current Source's label is initially positioned on the "Default Side" of the component. If you want, or need to change the position to improve the legibility, or layout of the circuit, you can set the position of the label to the "Other Side".