Question 5
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(a) State four effects of negative feedback on the output of an amplifier.
(b) Figure 3 is the circuit diagram of an operational amplifier.
Figure 3
Calculate the:- voltage gain;
- value of Vout.
Observation
The expected answers were:
-
(a) Effects of negative feedback in the output of an amplifier- Reduced gain;
- Reduced noise / interference;
- Increased bandwidth;
- Reduced distortion;
- Improved stability;
- Reduced output impedance / resistance
- Increased input impedance / resistance
(b) (i) Voltage gain
= 1 + 4
= 5
(ii) But
Vout = Av x Vin
= 5 x 10 mV
= 50 mV
Question 5 required candidates to state effects of negative feedback on the output of an amplifier and calculate voltage gain and Vout of an operational amplifier. The Chief Examiner reported that majority of the candidates that attempted this question did not respond well.