Question 8.11: The open-loop gain of a transistor amplifier is 1,000. The i...
The open-loop gain of a transistor amplifier is 1,000. The input and output impedances are 5 kΩ and 100 Ω, respectively. Calculate the voltage gain and input and output impedances when one percent negative feedback is incorporated.
Given,
A = 1,000
Z_{in} = 5 KΩ , Z_{o}=100 Ω
β= 0.01
Closed-loop voltage gain , A_{f}=\frac{A}{1+βA}=\frac{ 1,000}{1+0.01×1,000}
Z_{in} with feedback =Z_{in} (1 + βA)
= 5(1+0.01×1,000) KΩ
= 55 KΩ
Z_{0} with feedback =\frac{Z_{o} }{1+βA}=\frac{100}{1+0.01×1,000}=\frac{100}{11}
=9.9 Ω
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