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For transistor action
(a) Base, emitter and collector regions should have similar size and doping concentrations.
(b) The base region must be very thin and lightly doped.
(c) The emitter-base junction is forward biased and base-collector junction is reverse biased.
(d) Both the emitter-base junction as well as the base-collector junction are forward biased.
Which one of the following pairs of statements is correct?
(a) Base, emitter and collector regions should have similar size and doping concentrations.
(b) The base region must be very thin and lightly doped.
(c) The emitter-base junction is forward biased and base-collector junction is reverse biased.
(d) Both the emitter-base junction as well as the base-collector junction are forward biased.
Which one of the following pairs of statements is correct?
A
(d), (a)
B
(a), (b)
C
(b), (c)
D
(c), (d)
Detailed Solution
In a transistor the three regions differ in size and doping: the emitter is of moderate size and heavily doped, the base is very thin and lightly doped, and the collector is the largest and moderately doped. So (a) is wrong and (b) is correct.
The base is made thin and lightly doped so that very few of the majority carriers coming from the emitter recombine in it; most of them cross over to the collector.
For the transistor to work in the active region (as an amplifier), the emitter–base junction is forward biased and the base–collector junction is reverse biased. So (c) is correct and (d) is wrong.
Hence the correct pair is (b), (c).
The base is made thin and lightly doped so that very few of the majority carriers coming from the emitter recombine in it; most of them cross over to the collector.
For the transistor to work in the active region (as an amplifier), the emitter–base junction is forward biased and the base–collector junction is reverse biased. So (c) is correct and (d) is wrong.
Hence the correct pair is (b), (c).