NEIEP Mechanics Practice Exam

In an NPN transistor, what must be the bias condition of the base and emitter?

1. Reverse Bias

2. Unbiased

3. Floating Bias

4. Forward Biased

The correct answer is: Forward Biased

In an NPN transistor, the proper bias condition for the base and emitter junction is that the base must be forward biased relative to the emitter. This forward biasing is crucial for the transistor to operate effectively in its active region, which is where it can amplify signals. When the base-emitter junction is forward biased, it allows current to flow from the emitter into the base. This current flow is essential because it facilitates the movement of charge carriers (electrons) from the emitter into the base region. The presence of this base current allows for a much larger current to flow from the collector to the emitter, thus enabling the transistor to function as an amplifier. In contrast, if the base-emitter junction were reverse biased, it would not allow for current flow, effectively shutting down the transistor's ability to amplify signals. The unbiased and floating bias conditions also do not provide the necessary forward bias that allows for normal transistor operation. Hence, forward biasing is essential for the amplification and functioning of the NPN transistor.