Cascaded amplifiers -small signal model

Thread Starter


Joined Dec 25, 2004
Dear friends,
We say that we need to keep the input signal small in e.g. BJT amplifiers so that we don't lead the transistor in saturation. What is troubling me is if we connect two amplifiers in cascade and we keep the input signal small in the input of the first, won't the input signal in the second be very large, since the first amplifier amplifies that input? Why is there no problem with saturation there and we continue using the small signal models, eg two pi models in series?

Thank you very much in advance for any insight on this.


Joined Jan 22, 2004

before i go deep in answering your query of having a large signal introduced into the base of the 2nd transistor thru a capacitor, let me ask you a question.

have you tried biasing a transistor at unity gain or even less than unity or even a gain of 2? :)