An npn bipolar junction transistor (BJT) is operating in the active region. If the reverse bias across the base-collector junction is increased, thenThe effective base-width increases and common-emitter current gain increases The effective base-width increases and common-emitter current gain decreasesThe effective base-width decreases and common-emitter current gain increasesThe effective base-width decreases and common-emitter current gain decreases
Question
An npn bipolar junction transistor (BJT) is operating in the active region. If the reverse bias across the base-collector junction is increased, thenThe effective base-width increases and common-emitter current gain increases The effective base-width increases and common-emitter current gain decreasesThe effective base-width decreases and common-emitter current gain increasesThe effective base-width decreases and common-emitter current gain decreases
Solution
The correct answer is "The effective base-width increases and common-emitter current gain decreases".
Here's why:
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In an NPN transistor operating in the active region, the base-emitter junction is forward biased and the base-collector junction is reverse biased.
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When the reverse bias across the base-collector junction is increased, the depletion region at this junction widens. This effectively increases the base width because the base charge carriers (holes in this case) have a longer distance to travel to reach the collector.
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The increase in base-width reduces the base transport factor, which is the ratio of the number of carriers injected across the emitter-base junction that reach the collector to the total number of carriers injected from the emitter. This is because with a wider base, more carriers recombine within the base before they can reach the collector.
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The common-emitter current gain (β or hfe) is directly proportional to the base transport factor. Therefore, when the base transport factor decreases, the common-emitter current gain also decreases.
Similar Questions
A BJT is said to be operating in the saturation region ifBase-emitter junction is reverse biased and base-collector junction is forward biasedBoth the junctions are reverse biasedBoth the junctions are forward biasedBase-emitter junction is forward biased and base-collector junction is reverse biased
If the base width in a bipolar junction transistor is doubled, which one of the following statements will be TRUE?Current gain will increaseEarly voltage will increaseEmitter base junction capacitance will increaseUnity gain frequency will increase
For a common base configuration of npn transistor, collector current is greater than base current. Why?
A- The emitter injects holes into the base region Which of the following is VALID for both P-N-P as well as N-P-N transistor LO: PH.2.16 B- The electrons are the minority carriers in the base region C. The emitter base junction is forward biased for active operation - When a biased in the active region, current flows into their emitter terminal
What happens to the collector current (Ic) when the base current (Ib) increases in a BJT operating in the active region?
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