Question

In a transistor $\frac{I_C}{I_E}=\alpha$ and $\frac{I_C}{I_B}=\beta$. If $\alpha$ varies between $\frac{20}{21}$ and $\frac{100}{101}$, then the value of $\beta$ lies between:

• A. $1-10$
• B. $0.95-0.99$
• C. $20-100$
• D. $200-300$

Answer 1

Answer: (C)

$20-100$

We know that $I_E=I_B+I_C$

$⟹\frac{I_C}{\alpha }=\frac{I_C}{\beta }+I_C$

$⟹\beta =\frac{\alpha }{1-\alpha }$
Lower limit for $\beta =\frac{\frac{20}{21}}{1-\frac{20}{21}}=20$

Upper limit for $\beta =\frac{\frac{100}{101}}{1-\frac{100}{101}}$$=100$