GATE EE 2018 Set 1 — Question 25
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Analog & Digital Electronics → Operational Amplifiers → Ideal & Non-Ideal Op-Amp
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Question
The op-amp shown in the figure is ideal. The input impedance is given by
Correct answer
(B) -Z (R₂)/(R₁)
Solution
For an ideal op-amp, .
The current through is .
Since the inverting input current is zero, this same current flows through .
Thus, .
The input current is the current through impedance :
.
The input impedance is .
The current through is .
Since the inverting input current is zero, this same current flows through .
Thus, .
The input current is the current through impedance :
.
The input impedance is .
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