For a bipolar junction transistor (BJT) working as an amplifier, which of the following options is INCORRECT?

Explanation:

For a bipolar junction transistor (BJT) working as an amplifier, it is crucial to understand the correct biasing and connections of the terminals for both PNP and NPN configurations. Let's analyze the given options to identify the incorrect statement.

Correct Option Analysis:

The correct option is:

Option 2: For the collector junction of an NPN transistor, the P-terminal is connected to positive voltage, and the N-terminal is connected to negative voltage.

This option is incorrect because in an NPN transistor, the collector junction is typically reverse-biased when the transistor is operating in the active region (as an amplifier). In reverse bias, the N-terminal (collector) should be connected to a higher voltage (positive voltage), and the P-terminal (base) should be connected to a lower voltage (negative voltage). Therefore, the statement given in Option 2 contradicts this principle.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: For the emitter junction of a PNP transistor, the P-terminal is connected to positive voltage, and the N-terminal is connected to negative voltage.

This statement is correct. In a PNP transistor, the emitter junction is forward-biased when the transistor is in active mode. The P-terminal (emitter) is connected to a higher voltage (positive voltage), and the N-terminal (base) is connected to a lower voltage (negative voltage).

Option 3: For the emitter junction of an NPN transistor, the P-terminal is connected to positive voltage, and the N-terminal is connected to negative voltage.

This statement is correct. In an NPN transistor, the emitter junction is forward-biased when the transistor is in active mode. The P-terminal (base) is connected to a higher voltage (positive voltage), and the N-terminal (emitter) is connected to a lower voltage (negative voltage).

Option 4: For the collector junction of a PNP transistor, the N-terminal is connected to positive voltage, and the P-terminal is connected to negative voltage.

This statement is correct. In a PNP transistor, the collector junction is reverse-biased when the transistor is in active mode. The N-terminal (collector) is connected to a higher voltage (positive voltage), and the P-terminal (base) is connected to a lower voltage (negative voltage).

Conclusion:

Understanding the correct biasing conditions and terminal connections for PNP and NPN transistors is essential for their proper operation as amplifiers. The incorrect option (Option 2) misrepresents the correct biasing of the collector junction in an NPN transistor, leading to incorrect operation. Proper knowledge of these principles ensures the accurate functioning of BJTs in various electronic circuits.