A common-base stage has the following parameters: I C = 0.5 mA, C = 10 pF,

A common-base stage has the following parameters: I_C = 0.5 mA, C_π = 10 pF, C_μ = 0.3 pF, r_b = 200 Ω, β = 100, r_o = ∞, R_L = 0, and RS = ∞.

(a) Calculate an expression for the small-signal current gain of the stage as a function of frequency and thus determine the frequency where the current gain is 3 dB below its low-frequency value.

(b) Calculate the values of the elements in the small-signal equivalent circuits for the input and output impedances of the stage and sketch the magnitudes of these impedances from f = 100 kHz to f = 100 MHz using log scales.