Question

In common emitter configuration, \(\beta, \mathrm{R}_{\mathrm{L}}\) and r are the a.c. current gain, load resistance and the input resistance of a transistor respectively. The voltage and power gain respectively are

• A. \(\beta \frac{r}{R_{L}},\beta ^{2}\frac{r}{R_{L}}\)
• B. \(\beta \frac{\mathrm{r}}{\mathrm{R}_{\mathrm{L}}},\beta (\frac{\mathrm{r}}{\mathrm{R}_{\mathrm{L}}})^{2}\)
• C. \(\beta \frac{R_{L}}{r},\beta ^{2}\frac{R_{L}}{r}\)
• D. \(\beta \frac{R_{L}}{r},\beta (\frac{R_{L}}{r})^{2}\)

Hint:

Voltage gain is beta times R_L over r and power gain is the product of voltage gain and current gain.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
In common emitter configuration, the a.c. current gain is \(\beta\).

Step 2: Voltage gain
\(A_{V}=\beta\dfrac{R_{L}}{r}\).

Step 3: Power gain
\(A_{P}=\beta\times A_{V}=\beta^{2}\dfrac{R_{L}}{r}\).

Final Answer:
The voltage gain is \(\beta R_{L}/r\) and the power gain is \(\beta^{2}R_{L}/r\). \[ \boxed{\text{(C) }\beta \dfrac{R_{L}}{r},\ \beta^{2}\dfrac{R_{L}}{r}} \]