Question:medium
In common emitter transistor amplifier, the output resistance is \(500\) k\(\Omega\) and the current gain \(β = 50\). If power gain of amplifier is \(5\times 10^6\), what is the input resistance?
In common emitter transistor amplifier, the output resistance is \(500\) k\(\Omega\) and the current gain \(β = 50\). If power gain of amplifier is \(5\times 10^6\), what is the input resistance?
Show Hint
Power gain $=\beta^2\frac{R_{out}}{R_{in}}$.
Updated On: Oct 1, 2026
- \(325\Omega\)
- \(150\Omega\)
- \(350\Omega\)
- \(250\Omega\)
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Voltage gain route
Power gain $=$ current gain $\times$ voltage gain, so voltage gain $=\frac{5\times10^6}{50}=10^5$. Voltage gain $=\beta\frac{R_{out}}{R_{in}}$, so $\frac{R_{out}}{R_{in}}=2000$.
$R_{in}=\frac{500\times10^3}{2000}=250\,\Omega$.
Final Answer:
Option (D). \[ \boxed{\text{(D)}} \]
Power gain $=$ current gain $\times$ voltage gain, so voltage gain $=\frac{5\times10^6}{50}=10^5$. Voltage gain $=\beta\frac{R_{out}}{R_{in}}$, so $\frac{R_{out}}{R_{in}}=2000$.
$R_{in}=\frac{500\times10^3}{2000}=250\,\Omega$.
Final Answer:
Option (D). \[ \boxed{\text{(D)}} \]
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