Question

D11.5 Rpl 12 k 12 k R (c) + V₁ Figure 11.5.1 ۰۷ Rp Rgi 1200 120 R Figure 11.5.1 shows a series-shunt feedback amplifier known as a "feedback triplet." All three MOSFETs are biased to operate at gm = 5mA/V. You may neglect their ro's. (a) Select a value for Ry that results in a closed- loop gain Vo/V, that is ideally 12 V/V. (b) Determine the loop gain Aẞ and hence the value of Vo/V. By what percent does the closed- loop voltage gain differ from the value you designed for? How can you adjust the circuit to make Ay equal to 12? Section 11.4: Systematic Analysis of Feedback Voltage Amplifiers 11.6 V V Ru + ° + Figure 11.6.1 (a) Vi (b) Figure 11.6.1 continued A differential amplifier with a differential gain 1000 V/V, a differential input resistance. Rid 100 kn, and an output resistance ro = 1 k is shown in Fig. 11.6.1(a) with its equivalent cir- cuit in Fig. 11.6.1(b). To obtain a higher input resistance and a lower output resistance, series- shunt feedback is employed through a voltage divider (R1, R2), as shown in Fig. 11.6.1(c). For R₁ = 10 kn and R₂ = 90 k2, use the systematic feedback analysis method to determine the gain Vo/Vs of the feedback amplifier, its input resis- tance Rin, and its output resistance Rout. Also, if the gain is known to vary by 10% of its nomi- nal value, what is the variability of the gain of the feedback amplifier? 11.7 For the series-shunt feedback amplifier in Fig. 11.5.1, all three MOS transistors are operating at g 5 mA/V. You may neglect their ro's. (a) Select a value for Ry that results in a closed- loop gain Vo/V, that is ideally 12 V/V. (b) Use the systematic feedback-analysis proce- dure to determine the actual value obtained for Vo/V. Also, find the output resistance Rout2- Compare your results to those obtained using the loop-gain method in the solution to Problem 11.5. D11.8 Figure 11.4.1 shows a current-mirror-loaded dif- ferential amplifier to which series-shunt feedback is applied through the voltage divider (R1, R2), where R₁+R2470 k2. All MOSFETs have A 6V and are operated at Vorl 0.15 V. The input signal source has a zero de component. Use the systematic feedback-analysis method to determine the values of R1 and R2 that result in a closed-loop gain Va/V, of exactly 6 V/V. Also, determine the output resistance Reut. Compare your results to those obtained in the solution to Problem 11.4, where the loop-gain method is used.

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