EE3110 Bonus Question 3_1

EE3110 Bonus Question 3_1 - bootstrapping R 1 R 3 R 4 C 2 C...

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EE3110 Bonus Question 3: Bootstrapping. Due on Tuesday 21 st October before the start of lecture. It was shown in class that the effects of feedback are only valid at the summing point. The circuit shown in Figure BQ3A shows a typical common-collector (emitter follower) amplifier which is commonly used as a buffer. It can be viewed as a series-shunt feedback topology. A buffer amplifier has the characteristics of high input impedance and low output impedance. R 1 R 3 R 4 C 2 C 1 V CC v L v S R L R E R 2 Figure BQ3A Unfortunately resistors R1, R2, R3 and R4 limits the input resistance however much feedback you apply. The circuit shown in Figure BQ3B demonstrates how this limitation can be overcome by using a method known as
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Unformatted text preview: bootstrapping. R 1 R 3 R 4 C 2 C B 1 C B 2 C 1 V CC v L v S R L R E R 2 Analyze using both circuit theory and feedback theory how bootstrapping can increase the input impedance. To aid you in your analysis, follow the steps given below. 1) Draw the small-signal, a.c. equivalent circuit at mid-frequency for both circuits and compare their input impedance. 2) Draw the small-signal a.c. equivalent circuit at mid-frequency for both circuits without feedback and compare R i . 3) Determine β v and calculate the closed loop R if for both circuits....
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