A transistor is used as an amplifier in `CB` mode with a load resistance of `5 k Omega` the current gain of amplifier is `0.98` and the input resistance is `70 Omega`, the voltage gain and power gain respectively are

Options

A. (a)70, 68.6
B. (b)80. 66.6
C. (c)60, 96.6
D. (d)9, 96.6

Answer

To solve the problem step by step, we need to find the voltage gain and power gain of a transistor amplifier in common base (CB) mode.

### Step 1: Identify the Given Values
- Load Resistance, \( R_L = 5 \, k\Omega = 5 \times 10^3 \, \Omega \)
- Current Gain, \( \alpha = 0.98 \)
- Input Resistance, \( R_{in} = 70 \, \Omega \)

### Step 2: Calculate the Resistance Gain
The resistance gain \( R_g \) is given by the formula:
\[ R_g = \frac{R_L}{R_{in}} \]
Substituting the values:
\[ R_g = \frac{5 \times 10^3 \, \Omega}{70 \, \Omega} \]
Calculating this gives:
\[ R_g = \frac{5000}{70} \approx 71.43 \]

### Step 3: Calculate the Voltage Gain
The voltage gain \( A_V \) in common base mode is given by:
\[ A_V = \alpha \times R_g \]
Substituting the values we have:
\[ A_V = 0.98 \times 71.43 \]
Calculating this gives:
\[ A_V \approx 70 \]

### Step 4: Calculate the Power Gain
The power gain \( A_P \) is given by the product of the current gain and the voltage gain:
\[ A_P = \alpha \times A_V \]
Substituting the values:
\[ A_P = 0.98 \times 70 \]
Calculating this gives:
\[ A_P \approx 68.6 \]

### Final Results
- Voltage Gain, \( A_V \approx 70 \)
- Power Gain, \( A_P \approx 68.6 \)

### Conclusion
The voltage gain and power gain of the transistor amplifier in common base mode are approximately 70 and 68.6, respectively.

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