Question

For a transistor, the current ratio ${\alpha }_{dc}=\frac{69}{70}$. The current gain ${\beta }_{dc}$ is

• A. $66$
• B. $67$
• C. $69$
• D. $71$

Answer 1

Answer: (C)

$69$

Given : ${\alpha }_{dc}=\frac{69}{70}$

Current gain ${\beta }_{dc}=\frac{{\alpha }_{dc}}{1-{\alpha }_{dc}}$

$\therefore$ ${\beta }_{dc}=\frac{69/70}{1-69/70}$

$⟹$ ${\beta }_{dc}=\frac{69}{1}=69$