Engineering:Alpha cutoff frequency

Alpha cutoff frequency, or [math]\displaystyle{ f_{\alpha} }[/math] is the frequency at which the common base DC current gain [math]\displaystyle{ \alpha }[/math] drops to 0.707 of its low frequency value. The common base DC current gain is the ratio of a transistor's collector current to the transistor's emitter current, or [math]\displaystyle{ \alpha = \frac{i_C}{i_E} }[/math].