Frequency Response and Bandwidth

Coupling and bypass capacitors set a low-frequency cut-off; transistor and stray capacitances set a high-frequency cut-off. Bandwidth is $f_H - f_L$, measured at the −3 dB points (gain down to 70.7 %).

The Miller effect multiplies the base–collector capacitance by the gain, $C_{in} = C_{bc}(1 + |A_v|)$, which is often what limits the bandwidth of a common-emitter stage. Frequency response is drawn as a Bode plot.