Question

In a common emitter amplifier configuration, the current gain is 62. The collector resistance and input resistance are 5k$\Omega$ and 500$\Omega$ respectively. If the input voltage is 0.01 V, the output voltage will be ______.

• A. 0.62 V
• B. 6.2 V
• C. 62 V
• D. 620 V

Hint:

A transistor amplifier doesn't just amplify current; it relies heavily on transferring that current from a low-resistance input circuit to a high-resistance output circuit to achieve massive voltage amplification.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We are analyzing a Common Emitter (CE) transistor amplifier. We are given the AC current gain ($\beta$), the output/collector resistance ($R_c$), the input/base resistance ($R_i$), and the AC input voltage signal. We need to find the amplified AC output voltage.

Step 2: Key Formula or Approach:
1. The voltage gain ($A_v$) of a CE amplifier is the product of the current gain and the resistance ratio:
$$A_v = \beta \times \frac{R_{out}}{R_{in}} = \beta \times \frac{R_c}{R_i}$$
2. The output voltage ($V_{out}$) is simply the input voltage multiplied by the voltage gain:
$$V_{out} = A_v \times V_{in}$$

Step 3: Detailed Explanation:
Given parameters:
Current gain ($\beta$) = 62
Collector resistance ($R_c$) = 5 k$\Omega$ = $5000 \, \Omega$
Input resistance ($R_i$) = $500 \, \Omega$
Input voltage ($V_{in}$) = 0.01 V
First, calculate the resistance gain ratio:
$$\text{Resistance Gain} = \frac{R_c}{R_i} = \frac{5000}{500} = 10$$
Next, calculate the total voltage gain ($A_v$):
$$A_v = \beta \times \text{Resistance Gain} = 62 \times 10 = 620$$
Finally, calculate the output voltage:
$$V_{out} = A_v \times V_{in}$$
$$V_{out} = 620 \times 0.01 = 6.2 \text{ V}$$

Step 4: Final Answer:
The output voltage will be 6.2 V, matching option (b).