feedback doublt

[tamashii]

I have a question concerning feedback circuits. Usually, for analyzing the circuit, we want to get all load effects inside the basic amplifier network (thus, reaching the 'ideal' case where there are no impedances in the circuit but inside the basic amplifier); but is it always necessary to put the source and load resistances inside it or can we leave them out?

 

[Russlk]

You need to include all parts that affect the gain or phase. If the source impedance is low enuf relative to the input impedance of the amp, it could be neglected. Likewise, if the load impedance is high relative to the output impedance of the amp, it could be neglected.

 

[tamashii]

I assume those approximations are only for the series-shunt configuration, but what I meant was, can we leave them out to analyze the feedback loop, and then include them next to the feedback equivalent circuit?

 

[Russlk]

What is the point? Why would you want to do that?

 

[tamashii]

just to isolate the two-port network, so that it could work for any load and source recistance we attached to it