Current Frequency:

At microwave frequency performance of the transistor is depends on its cut-off frequency rather than its gain.

$f_c=\text{cut off frequency=}\dfrac{1}{2πτ} \\ τ=\text{total transist time=}τ_c+τ_b+τ_c+τ_d \\ τ_0=\text{emitter base junction transit time} \\ τ_b=\text{Base transit time.} \\ τ_d+τ_c=\text{colector junction time.} \\ ∴f_{\max}=\sqrt{\dfrac{f_c}{8 \pi γ_b' C_c}} \\ γ_b'=\text{base resistance} \\ C_c=\text{collector …