Consider the diff-amp with active load in Figure P11.66. The Early voltages are \(V_{A N}=120 \mathrm{~V}\) for \(Q_{1}\) and \(Q_{2}\) and \(V_{A P}=80 \mathrm{~V}\) for \(Q_{3}\) and \(Q_{4}\).

(a) Determine the open-circuit differential-mode voltage gain.

(b) Compare this value to the gain obtained when \(R=0\).

(c) Determine the output resistance \(R_{o}\) for parts

(a) and (b). Assume \(\beta=100\). [Hint: As a good approximation, use the output resistance results from a Widlar current source.]

V+ = 10 V R = 1 ks R = 1 k Q3 Q4 Q Q2 = 0.2 mA V-= -10 V Figure P11.66