Test: Operational Amplifier - Electronics and Communication Engineering (ECE) MCQ

- Common-Mode Rejection Ratio (CMRR) is a key parameter in differential amplifiers, measuring its ability to reject common-mode signals, which are signals that appear simultaneously on both inputs.
- CMRR is defined as the ratio of differential gain to common-mode gain.
- Ideally, the differential amplifier should amplify only the difference between the input signals, not the common signals.
- A CMRR of infinity means the amplifier perfectly rejects all common-mode signals, which is the ideal scenario.

Given circuit represents an inverting summer using op-amp
Here,

R = R₁ = R₂ = R₃ = R_f = 1 kΩ

and

V₁ = +2 V, V₂ = +3 V, V₃ = +4 V

The output voltage is

Using superposition theorem, the output voltage is given by

The time period of the given a stablem ultivibrator circuit is given by

For an ideal OPAMP, input impedance is infinite while output impedance is zero.

Given op -amp circuit re p re se n ts a c losed -loop non -inverting amplifier. The feed back factor is given by

For a practical OPAMP in put impedance is of the order of 10⁶Ω

We know that

An ideal operational amplifier has

• zero offset voltage
• characteristics which do not drift with temperature
• infinite voltage gain
• infinite CMMR
• infinite bandwidth

Hence, statements 2 , 3 and 5 are only correct.