Question

Assertion :In a common-emitter amplfier, the load resistance of the output circuit is 1000 times the load resistance of the input circuit. If $\alpha =0.98$, then voltage gain is $49\times {10}^3$ Reason: $\alpha =\frac{\beta }{1-\beta }$ (symbols have their usual meaning).

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

$\alpha =\frac{i_c}{i_e}$

and $\beta =-\frac{i_c}{i_b}$

and $i_c+i_b=i_e$

$⟹\frac{1}{\alpha }-\frac{1}{\beta }=1$

$⟹\alpha =\frac{\beta }{1+\beta }$

Voltage gain=$\frac{v_{out}}{v_i}=\frac{i_c{R}_c}{i_b{R}_b}$

$=1000\times \frac{i_c}{i_b}$
$=1000\times 49$