Question

Consider the op-amp configuration shown in the figure below:


Assume the op-amp circuit to be ideal, then which of the following statements is not correct about the circuit ?

• A. The circuit represents an integrator circuit with output having a phase shift of ${180}^o$
• B. The circuit introduces an input capacitance nearly equal to the value of capacitance C.
• C. The value of input is reduced by a factor of (RC) and is integrated
• D. The value of time constant for the circuit $\tau$ = RC

Answer 1

The correct option is B The circuit introduces an input capacitance nearly equal to the value of capacitance C.

The value of input capacitance is equal to

$C_{in}=C(1-A_v)$ (Miller's theorem)

$\because$ The op-amp is ideal and inverting
$C_{in}=\infty$