My question concerns multi-stage amplifiers and small-signal analysis. We use small-signal analysis because the response of an amplifier over a small range of input voltages is approximately linear. In one of the lectures, Professor Agarwal mentions using another amplifier stage in series with the first stage to get more gain. How does this work within the confines of the small signal model? It seems to me that the amplified signal would be too large to have a linear response in the following stage. Detailed responses are welcomed, thank you.

Question

My question concerns multi-stage amplifiers and small-signal analysis.  We use small-signal analysis because the response of an amplifier over a small range of input voltages is approximately linear.  In one of the lectures, Professor Agarwal mentions using another amplifier stage in series with the first stage to get more gain.  How does this work within the confines of the small signal model?  It seems to me that the amplified signal would be too large to have a linear response in the following stage.  Detailed responses are welcomed, thank you.

kenljw · Answer

If the input is small enough you can add more stages of amplification without distortion.  Also with multi-stages you can add feedback which also decreases overall gain but increases bandwidth.