Transistor in a circuit basically acts as:

Explanation

A Transistor is a device which consists of three regions of doped semiconductors in which the current flowing is modulated by the voltage or current applied to one or more electrodes. These includes: Emitter- Heavily doped and function is to emit the charges. Collector- Moderately Doped and function to collect the charges Base- Lightly Doped and functions to reduce the transit time of charge. In PN Transistors there are two types: NPN - in which electrons are majority charge carriers (these are most widely used as the mobility of electrons is three times more than the holes and operation is faster within these transistors) PNP- in which holes are majority charge carriers A Transistor works as an amplifier by increasing the strength of the signal. A signal can be used to refer to any particular current, voltage, or power in a circuit. BUT... within these transistors there are three types of configurations: Common Emitter Configuration, Common Base Configurations and Common Collector Configurations Among these configuration Common emitter configurations is the most widely used (Book Statement KPK/FTB Pg no 246). Common emitter configurations are used when large current gains are needed, therefore for this MCQ, Current Amplifier is the most preferable option.