Question

If the current amplification factor for a transistor connected in common emitter configuration is $100$ and input resistance is $200\Omega$, then calculate the power gain

• A. $4\times 10^4$
• B. $5\times 10^3$
• C. $7\times 10^3$
• D. $45\times 10^4$

Answer 1

Answer: (A)

$\alpha =100,R_{BE}=200,R_L=800\Omega$
power gain $=$ Voltage gain $\times$ current gain
$\beta =\frac{\Delta I_C}{\Delta I_B}$
$\frac{V_o}{V_i}=\beta \frac{R_L}{R_{BE}}$
$\Rightarrow \text{ Power gain }=\beta \frac{R_L}{R_{BE}}\beta$
$={\beta }^2\frac{R_L}{R_{BE}}=(100{)}^2\frac{800}{200}$
$=4\times 10^4$