waecE-LEARNING
Electronics Paper 2, May/June 2012  
Questions: 1 2 3 4 5, 6 &7 8 9 10 Main
General Comments
Weakness/Remedies
Strength
















Question 3
  1. An amplifier has an input signal of 1 mA at 10 mV and a corresponding output signal of 10 mA at 1 V. Calculate the:
  2. voltage gain;
  3. current gain;
  4. power gain.
  1. Calculate, in decibels, the gains obtained in (a).


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OBSERVATION

The expected answers were:
(a)      (i)      Voltage gain = 
                                      =       
                                      =  100                  
                    (ii)      Current gain  =
                                      =       
                                      =  10 
                    (iii)     Power gain   =  Voltage gain  x  Current gain
=  100  x  10
=  1000
(b)     (i)      Voltage gain in dB   =  10 log 100 10
                                                          =  20 dB     
                    (ii)      Current gain in dB   =  10 log 10 =  10 dB
                    (iii)    Power gain in dB    =  10 log 1000

                                                          =  30 dB

Surprisingly, most of the candidates could not answer this question correctly.
The question was on Amplifiers. The question was attempted by many candidates. The performance was average.

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