Question

For the circuit shown below:

For a nominal gain of 4, a gain error of 0.1% and an input impedance of at least 10 $k\Omega$, the value of resistance $R_1$ is _____ $k\Omega$ and op-amp gain is ________.

• A. 20 and 2000
• B. 40 and 5000
• C. 50 and 2000
• D. 10 and 5000

Answer 1

The correct option is B 40 and 5000

Since both the nominal gain and the gain error are given, we must first determine the minimum op-amp gain we have
$\frac{R_1}{R_2}=4$
$\frac{1}{A_0}(1+\frac{R_1}{R_2})=0.1\%$

Thus, $A_0=5000$
Since, the input impedance is approximately equal to $R_2$ , We choose,
$R_2$ = 10 $k\Omega$
and $R_1$ = 40 $k\Omega$