The correct answer is: All of the mentioned.
A bipolar transistor is a three-terminal semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor’s terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.
Bipolar transistors can be either NPN or PNP type. The difference between these two types is the polarity of the charge carriers. In an NPN transistor, the majority charge carriers are electrons, while in a PNP transistor, the majority charge carriers are holes.
When a small voltage is applied to the base-emitter junction of a bipolar transistor, it causes a large current to flow through the collector-emitter junction. This is because the base-emitter junction is forward-biased, while the collector-emitter junction is reverse-biased. The forward bias causes a large number of electrons to be injected into the base region. These electrons then diffuse into the collector region, where they are collected by the collector electrode. The current that flows through the collector-emitter junction is much larger than the current that flows through the base-emitter junction. This is the principle of transistor action.
The turn-on delay of a bipolar transistor is the time it takes for the transistor to start conducting current when a voltage is applied to the base-emitter junction. The turn-off delay is the time it takes for the transistor to stop conducting current when the voltage is removed from the base-emitter junction. The storage time is the time it takes for the charge carriers to be removed from the base region after the voltage is removed from the base-emitter junction.
The turn-on delay, turn-off delay, and storage time are all important factors in the performance of a bipolar transistor. The turn-on delay determines how quickly the transistor can respond to a change in input signal. The turn-off delay determines how quickly the transistor can stop conducting current when it is no longer needed. The storage time determines how long the transistor will continue to conduct current after the input signal is removed.
The turn-on delay, turn-off delay, and storage time of a bipolar transistor can be affected by a number of factors, including the temperature, the type of semiconductor material used, and the design of the transistor.