If the gain of a closed-loop inverting amplifier is 3.9 (magnitude) with an input resistor value of 1.6 K ohms, what value of feedback resistor is necessary ?

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LPSC ISRO Technical Assistant Electronics 07 Aug 2016 Official Paper
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  1. 2.4 K ohms
  2. 6.24 K ohms
  3. 0.62 K ohms
  4. 410 ohms

Answer (Detailed Solution Below)

Option 2 : 6.24 K ohms
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Detailed Solution

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Concept:

F1 S.B Madhu 10.07.20 D2

For an inverting amplifier, as shown above, the voltage gain is given by:

\(A_v=\frac{V_0}{V_{in}}=-\frac{R_f}{R_i}\)

Ri = Input resistance

Rf = Feedback resistance

Calculation:

Given Av = 3.9 and Rin = 1.6 kΩ

\(3.9=\frac{R_f}{1.6k}\)

Rf = 3.9 × 1.6k

Rf = 6.24 kΩ

Important Point:

F1 S.B Shubham 02.06.20 D 15

The voltage gain of a non-inverting amplifier is given by:

\({A_v} = 1 + \frac{{{R_2}}}{{{R_1}}}\)

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