(a) Calculate the loop gain T = af for the series-shunt feedback circuit in Fig. 8.59 using hparameter two-ports. Take R₁= 200 kΩ, and R₂= 100 kΩ. For the op amp, assume R_i= 50 kΩ, R_o= 1 MΩ, and a_v= 1 × 10³.

(b) If the input source location and type in Fig. 8.59 are changed as shown in Fig. 8.61, the feedback is now shunt-shunt. Calculate the loop gain T = af for this shunt-shunt feedback circuit using y-parameter two-ports. Use the element values in (a).

(c) Calculate the return ratio R for the circuit in Fig. 8.61, again using the element values in (a). This return ratio is the same as the return ratio for the circuit in Fig. 8.59. Why?

(d) Compare the results in (a), (b), and (c).

Fig. 8.59:

Fig. 8.61:

V; R2 w- V. +, R2 V. R4