The circuit in Figure P12.51 is an example of a shunt-series feedback circuit. A signal proportional to the output current is fed back to the shunt connection at the base of \(Q_{1}\). However, the circuit may be used as a voltage amplifier. Assume transistor parameters of \(h_{F E}=120, V_{B E}(\mathrm{on})=0.7 \mathrm{~V}\), and \(V_{A}=\infty\).

(a) Determine the small-signal parameters for \(Q_{1}\) and \(Q_{2}\).

(b) Using nodal analysis, determine the small-signal voltage gain \(A_{v}=v_{o} / v_{s}\).

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Vcc = 10 V ww Cc ww R = 38.3 ww Rs = 0.6 k Us Figure P12.51 ww Rc = 3 kQ R = 13.5 REI www Rc2=4k Q2 RE2= 8.1 Rp = 1.2 kQ ww CF00