Question

12.8

250, and Pr Contributed by Qc 0D 01 02 O DOUT 03 04 Qs QA QB Rs RI VEE-15V Figure P12.8 800 Chapter 12 Analog Integrated Circuits 12.8 The circuit of Fig. P12.8 illustrates a simple BJT op-amp that resembles the input stage of the LM741. It consists of a differential input stage a class A voltage-follower output stage formed by Qs the collector of 12.10回 Considerthetwo-stageBrt㎎ to yield a differential gain of a las-fa ascaded with a class in Fig, P12.8. Choose appropriate valuen ie (a) Choose values for Rref and Ri such that the bias value for vOUT of approximately zero The BiFET (bipolar-FET) currents through R2 and R, are both set to approx 12.11 imately 50μΑ P12.11 uses BJTs and JFETs together nt (b) Choose values for R2, R3, Ra, and Rs such that(a) Find expressions for lat Iand vOUT is biased at approximately zero. (b) Find expressions for the voltags of e E in terms of Vy and other paranetens (c) Use the expression for the voltage ofisik E an approximate expressin fr la 12.9 Consider the circuit of Fig. P12.8 that depicts a sim- pel two stage BT orp amp Suppose that Ri and Ret are tc) Uise bhe exprssiono chosen so that the current through QB is about 100μA. If 03. Q4, R2, and R3 are omitted from the circuit, and the emitters of Qi and 02 connected directly to the col- (d) Apply KCL at the outpsut lector of QB, find the resulting bias voltage measured at node for the bias value of voOUT

Answer 1

Dl From te Circat der to inde Value e havr to cheos d n re -15-o. e tmA

too nd 2 malee Ve Te IS-O おう 2 5 ← l2 s