A BJT current gain amplifier is shown in Figure P12.48. The transistor parameters are \(\beta_{1}=\beta_{2}=180, V_{A 1}=V_{A 2}=\infty\), and \(I_{S 1}=I_{S 2}=10^{-15} \mathrm{~A}\). The LED turn-on voltage is \(V_{\gamma}=1.6 \mathrm{~V}\). Assume the LED small-signal resistance is \(r_{f}=0\).

(a) Determine the quiescent currents \(I_{C Q 1}\) and \(I_{C Q 2}\).

(b) Derive the expression for the small-signal current gain \(A_{i}=I_{o} / I_{i}\).

(c) Calculate the value of \(A_{i}=I_{o} / I_{i}\).

Transcribed Image Text:

Figure P12.48 V+= 5 V Rc=200 ww Q1 22 VR=3.6 V ww Rp=500 2 LED 10= 16 mA