Figure 112 $\mu=10^{3}$ , Input Resistance $R_{i d}=100 \mathrm{k} \Omega$ , and Output Resistance

Figure 11.2.1
The series-shunt feedback amplifier shown in Fig. 11.2.1 utilizes a differential amplifier with a gain $\mu=10^{3}$ , input resistance $R_{i d}=100 \mathrm{k} \Omega$ , and output resistance $r_{o}=1 \mathrm{k} \Omega$ . The feedback amplifier is fed with a signal source $V_{S}$ having a source resistance $R_{S}=10 \mathrm{k} \Omega$ , and a load resistance $R_{L}=$ $1 \mathrm{k} \Omega$ is connected to the output terminal.
(a) If it is required to obtain a closed-loop gain $A_{f} \equiv V_{o} / V_{S}$ that is ideally $10 \mathrm{~V} / \mathrm{V}$ , what is the required feedback factor $\beta$ ? If $R_{1}=1 \mathrm{k} \Omega$ , what value must $R_{2}$ have?
(b) Give the complete $A$ circuit and use it to determine $A, R_{i}$ , and $R_{o}$ .
(c) Find the actual value of $A_{f}$ realized.
(d) Find the input resistance $R_{\text {in }}$ of the feedback amplifier.
(e) Find the output resistance $R_{\text {out }}$ of the feedback amplifier.
(f) If, due to temperature variation, the gain $\mu$ changes by $10 \%$ , what percentage change do you expect $A_{f}$ to have?
(g) If the high-frequency response of the amplifier $\mu$ is characterized by a drop of $20 \mathrm{~dB} /$ decade with a 3-dB frequency of $10 \mathrm{kHz}$ , what do you expect the 3-dB frequency of the gain $A_{f}$ to be? At what frequency will the magnitude of $A_{f}$ become unity?

Correct Answer:

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Figure 11.2.1
(a) For to be ideally ...

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