Q. Give an account on the operation of the R-C coupled amplifier.

When a.c. signal is applied to the base of the first transistor, it appears in the amplified form across its collector load Rc. The amplified signal developed across Rc is given to base of next stage through coupling capacitor Cc. The second stage does further amplification of the signal. In this way, cascaded stages amplify the signal and the overall gain is considerably increased.

It may be mentioned here that total gain is less than the product of the gains of individual stages. It is because when a second stage is made to follow the first stage, the effective load resistance of first stage is reduced due to the shunting effect of the input resistance of the second stage. This reduces the gain of the stage, which is loaded by the next stage. For instance, in a 3-stage amplifier, the gain of first and second stages will be reduced due to loading effect of next stage. However, the gain of the third stage, which has no loading effect of subsequent stage, remains unchanged. The overall gain shall be equal to the product of the gains of three stages.