NEIEP Mechanics Practice Exam

A 0.7 V drop from base-to-emitter in a transistor, specifically a silicon bipolar junction transistor (BJT), indicates that the transistor is functioning normally. This voltage drop is characteristic of the forward bias condition necessary to allow current to flow from the base to the emitter. When the base-emitter junction is forward biased, it allows the transistor to conduct, enabling it to perform its function in a circuit.

If the voltage drop were significantly lower than 0.7 V, it might suggest that the junction is not adequately forward biased, which could indicate issues such as a faulty component or an open circuit. Conversely, if the voltage drop were considerably higher, it might imply that the junction is not functioning properly, possibly due to a short circuit. Therefore, a base-emitter voltage drop of around 0.7 V confirms that the junction is in good working condition, hence supporting the conclusion of a good junction.