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Question: Answered & Verified by Expert
In a transistor, the value of $\alpha$ varies between $\frac{20}{21}$ and $\frac{100}{101}$. Then the value of $\beta$ varies between
PhysicsSemiconductorsAP EAMCETAP EAMCET 2019 (20 Apr Shift 2)
Options:
  • A 1 and 10
  • B 0.95 and 0.99
  • C 20 and 100
  • D 200 and 300
Solution:
2892 Upvotes Verified Answer
The correct answer is: 20 and 100
Given, in a transistor current gain,
$$
\alpha=\frac{20}{21} \text { and } \frac{100}{101}
$$

Now, common emitter transistor
DC current gain, $\beta=\frac{\alpha}{1-\alpha}$
Case I If $\alpha=\frac{20}{21}$, then $\beta=\frac{\frac{20}{21}}{1-\frac{20}{21}}=20$
Case II $\alpha=\frac{100}{101}$, then $\beta=\frac{\frac{100}{101}}{1-\frac{100}{101}}=100$
$\therefore$ Value of $\beta$ varies between, $\beta \in[20,100]$.

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