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Electronics Paper 2, Nov/Dec. 2009  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments

Question 3

State two advantages and two disadvantages of RC coupling in amplifiers.
  • (i)  Explain the need for the use of negative feedback in amplifier circuits.
  • (ii) State two advantages and one disadvantage of negative feedback.

The expected answers were:

Advantages of RC coupling

  • d.c. isolation between stages;
  • simple circuitry;
  • has less frequency distortion.

                             Disadvantages of RC coupling
                             (i)      low overall amplifier gain in multistage design;
                             (ii)      tendency to become noisy with age;
                             (iii)     poor resistance (impedance) matching.

  • (i) Negative feedback is introduced in amplifiers to maintain the stability of its operating parameters.

(ii)    Advantages of negative feedback

  • Reduction of noise
  • Reduction of distortion
  • Stability of operating parameters
  • Input and output impedance can be modified as desired
  • Increase bandwidth.

Disadvantage of negative feedback

  • Reduced gain

The question was on amplifiers.  Few candidates attempted the question. The performance was average.
The question had two parts; the first part is the purely recall question of stating the advantages of RC-coupling in transistor amplifiers, and the second, another purely recall question, requiring the merits of feedback in amplifier.


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