Figure P7.62 shows the high-frequency equivalent circuit of an FET, including a source resistance \(r_{s}\).

(a) Derive an expression for the lowfrequency current gain \(A_{i}=I_{o} / I_{i}\).

(b) Assuming \(R_{i}\) is very large, derive an expression for the current gain transfer function \(A_{i}(s)=I_{o}(s) / I_{i}(s)\).

(c) How does the magnitude of the current gain behave as \(r_{s}\) increases?

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Cgd -OV R V + g8 8mV R www Figure P7.62