please answer all parts then find the impedences. TD is loop gain and TN is feed

Question

please answer all parts then find the impedences.

TD is loop gain and TN is feedforward ratio

Suppose we attempt to create a feedback circuit using a bjt, by copying an op-amp circuit. See figure 3.3. a.) Show that G- b) Show that Ty-oo. c.) Show that TD TR., Hint: Find o' in two ways; i) in terms of ib by considering the circuit between vs and the emitter, and ii.) by finding the total current through R1. Why is TD not large? What happens if we find To approximately, ignoring all terms in the denominator except the term pR1? 2s Lour lont Lx Figure 3.3: A bjt circuit is made by copying an op-amp circuit. Find the input and output impedances in the previous example

Explanation / Answer

i ) By using KCL and KVL , we get different equations -

i' = ib + B (beta) ib = (1+B) ib

v' = (i' + iout ) * R1 = ((1+B)ib + iy)* R1

vs - (Rs+rpi)* ib = v'

ii) By virtual ground theory the voltage at the junction of feedback of opamp is Vs and as no current can go inside or can come out from opamp so total current through R1= iout=Vout/RL

a) Now considering Go as the feedback gain of the opamp we have ,

Go= Vout/Vs which can be calculated by considering the currents in both the resistors to be equal,

Vout/RL= VS/R1

so Go=Vout/VS= RL/R1 (The voltage along R1 be equal to Vs due to the virtual ground theory which says the voltage at both the terminals of opamp is equal)

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