Bandwidth of a multistage amplifier
The range of frequencies which are amplified without much variation in gain is called bandwidth of amplifiers.
Human ears are insensitive to the variation of power gain of about 3dB. Hence, frequency range from lower 3dB to upper 3dB is considered as bandwidth of single stage amplifier.
Bandwidth of single stage amplifier.
Bandwidth (BW) = fH – fL ~ fH
Upper 3dB frequency of multistage amplifier
Identical nun-interacting single stage
If fH* is the upper 3dB frequency of multistage amplifier then
At f = fH* from (2) & (3)