Semiconducting Devices Question 18
Question: Assertion : Base in a transistor is made very thin as compared to collector and emitter regions. Reason : Due to thin base power gain and voltage gain is obtained by a transistor.
Options:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.
Show Answer
Answer:
Correct Answer: A
Solution:
In a transistor, the base is made extremely thin to reduce the combinations of holes and electrons.
Under this condition, most of the holes (or electrons) arriving from the emitter diffuses across the base and reach the collector.
Hence, the collector current, is almost equal to the emitter current, the base current being comparatively much smaller.
This is the main reason that power gain and voltage gain are obtained by a transistor.
If the base region was made quite thick, then majority of carriers from emitter will combine with the carriers in the base and only small number of carriers will reach the collector, so there would be little collector current and the purpose of transistor would be defeated.
