Which of the following statements is NOT correct about Bipolar Junction Transistors?

14) Which of the following statements is NOT correct about Bipolar Junction Transistors? 

1. Emitter follower configuration will always have an output voltage slightly less than the input signal. [Option ID = 2885]
2. Common-base configuration has very low input impedance. [Option ID = 2886]
3. The CE emitter-bias configuration with an unbypassed emitter resistor has a larger input resistance than the bypassed configuration. [Option ID = 2887]
4. The voltage divider bias configuration has much less stability than the fixed-bias configuration. [Option ID = 2888]

Answer: A

Solution

To find the statement that is NOT correct, we evaluate each based on transistor theory:

Statement	Engineering Fact	Status
1. Emitter Follower output < input	Voltage gain is always slightly less than unity (approx. 0.98).	CORRECT
2. CB has low input impedance	Input resistance is approximately re (very small).	CORRECT
3. Unbypassed RE increases Rin	The unbypassed resistor adds βRE to the input impedance.	CORRECT
4. Voltage Divider is less stable than Fixed Bias	Voltage Divider is the most stable bias; Fixed Bias is the least stable.	NOT CORRECT

Conclusion: Statement 4 is factually false because Voltage Divider bias is designed specifically to provide superior thermal and β stability compared to Fixed Bias.

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