Simulating dependent sources

Oct 12, 2008 2 Replies

I'm writing a circuit simulation program as an exercise and I'm using the nodal method. The nodal method requires every branch current to be a function of some branch voltage so the circuit can be solved through the KCL.



What do we do with dependent voltage sources though? The only way I can think of implementing them is by transforming them into current sources, but that needs a resistor in series of the voltage source.


Some exercise...

This is a standard problem, and is solved in spice by using "Modified Nodal Analysis" (MNA) as standard.

I would recomend the book "The Spice Book" by Andrei Vladimirescu ISBN

0-471-60926-9

Quoting bits and bobs from p.281-282

The Matrix equation

|G||V| = |I|

is replaced by

|G F| |V| = |C| |B R| |I | |E|

To wit, "problem.. voltage sources...can not be included....this lead the developers of spice to extend the set of nodal equations to include voltage source equations represented by currents in the unknown vector and by voltages in the RHS vector."

I will leave you to figure out the details of above..

Kevin Aylward

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- SuperSpice

I know nothing of simulations, but all voltage sources have a series reistance. A "good" voltage source has a low series reistance, as a "good" current source has a large parallel resistance.

George Herold

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