Consider the BiMOS differential amplifier circuit illustrated in Fig. P12.4. (BiMOS means the circuit contains both bipolar and MOS devices.) The pnp transistors have a forward beta β_F  of 50 and Early voltage V_A of 20 V. The base-emitter voltage V_BE is  -0.6 V in the forward active region, and the transistors saturate when the emittercollector voltage VEC is less than 0.2 V. The npn transistors have a forward beta β_F of 100 and Early voltage of -60 V. The base-emitter voltage V_BE is 0.6 V in the forward active region, and the transistors saturate when the collector-emitter voltage VC- is less than 0.2 V. The n-channel MOSFETs have a K-factor of 100 pA/V², threshold voltage V, of 1.0 V, and Early voltage V’ of 10 V.

(a) Select R to yield a quiescent collector current in Q6 of 0.1 mA. (Assume that Q5 and Q6 are identical transistors.)

(b) With R as in part a and with v_IN1 = vI_N2 = 0, what is the gate-to-source voltage V_GS on Q₃?

(c) What is the maximum possible common mode input voltage for which the transistors will be operating in their forward active regions?

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