Question 5
- State four applications of operational amplifier.
- A non-inverting op-amp has the following parameters:
Ri = 3 kΩ;
Rf = 100 kΩ.
Open loop gain (A) = 500,000.
Calculate the:
- Feedback ratio (β);
- Loop gain.
The expected answers were:
(a) Common applications of the operational amplifier
- Inverting amplifier
- Non-inverting amplifier
- Phase shifter
- Scale Changer
- Differential Amplifier / comparator
- Differentiator
- Integrator
- Summing amplifier
- Voltage-to-current converter
- Current-to-voltage converter
(b) (i) The feedback ratio is given by
(ii) And the CLOSED loop-gain, by
The Chief Examiner reported that majority of the candidates that sat for this paper avoided this question and that the responses of the few candidates that attempted it were poor. Therefore, concept of operational amplifier can easily be considered as an area of weakness of the candidates.