Question:
Which of the following statements is/are true for a BJT with respect to its DC current gain \(\beta\)?
Which of the following statements is/are true for a BJT with respect to its DC current gain \(\beta\)?
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The current gain \(\beta\) of a BJT is influenced by injection levels, recombination in the base, and the region of operation. Carefully analyze these factors to determine changes in \(\beta\).
Updated On: Jan 31, 2025
- Under high-level injection condition in forward active mode, \(\beta\) will decrease with an increase in the magnitude of collector current.
- Under low-level injection condition in forward active mode, where the current at the emitter-base junction is dominated by recombination-generation process, \(\beta\) will decrease with an increase in the magnitude of collector current.
- \(\beta\) will be lower when the BJT is in saturation region compared to when it is in active region.
- A higher value of \(\beta\) will lead to a lower value of the collector-to-emitter breakdown voltage.
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The Correct Option is A
Solution and Explanation
Statement 1 (True):
In high-level injection conditions, the base transport factor decreases due to increased carrier recombination in the base region. This results in a reduction in the current gain \(\beta\).
Statement 2 (False):
During low-level injection, the emitter efficiency and base transport factor remain nearly constant, and recombination-generation effects are minimal. Consequently, \(\beta\) does not significantly decrease as collector current increases.
Statement 3 (True):
In the saturation region, both the base-emitter and base-collector junctions are forward-biased, leading to a higher recombination rate in the base. This reduces the current gain \(\beta\) compared to its value in the active region.
Statement 4 (True):
A higher \(\beta\) implies a reduced base current for a given collector current, increasing the likelihood of breakdown. This results in a lower collector-to-emitter breakdown voltage for the BJT.
Final Answer:
\[
\boxed{{(1, 3, 4) or A, C, D}}
\]
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