Comparison Between BJT and FET Operation
BJT and FET both have different operations . In BJT both minority and majority charge carriers are responsible for the flow of current .In BJT emitter base junction is forward biased and the collector base junction is reverse biased. In NPN transistor due to less barrier potential in base emitter junction the electron flow from emitter to base and in base only few electron combine with holes because base is lightly doped and have fewer holes and this flow of electron leads to base current .The remaining electron from base region flows to reverse biased collector junction and leads to collector current .according to KCL .
IE = IB + I C
IE = Emitter Current , IB = Base Current , IC = Collector Current
Working of PNP is same as NPN but majority charge carriers are holes in PNP transistor .
BJT operates in three different regions based on the biasing of the junctions :
- Active Region : In this region emitter base junction is forward biased and collector base junction is reverse biased . Transistor works as amplifier in this region.
- Saturation Region : In this region both emitter base junction and collector base junction is in forward bias .Transistor work as switch in this region.
- Cut-off Region : In this region both emitter – base junction and collector base junction is in reverse bias . Transistor is OFF in this region.
where as FET is unipolar device in this only majority charge carriers are responsible for flow of current . FET have drain , gate , source and channel . The majority charge carriers enters from source and passes from channel and leads to drain . Therefore the current direction is from drain to source . The voltage applied in gate terminal is responsible for the amount of current that flows through channel that’s why FET is called voltage controlled device.
Difference Between BJT and FET
The transistor is a three-terminal semiconductor device, it is an active device that is used in most of the electronics devices. Transistors can be used as insulators and as conductors as needed. we can use a transistor as a switch and as an amplifier. It can be used with other circuit elements and can be able to amplify current and voltage. We can classify transistors into two types that is Bipolar, and Field Effect Transistor.
BJT is a three-terminal device, it has two PN junctions. It is mostly used analog electronic device because of its high current gain. FET is a very important component in today’s electronic devices. FET is a type of device in which electric fields are used to control the flow of charges or current flowing through a channel. Due to its high input impedance, low output impedance, and high gain capacity, they are widely used in electronic devices.
BJT and FET both are used in many different devices and they have many different characteristics that make them different from each other. In this article, we will go through all the things that make them different and we will get the overview of BJT and FET.
Table of Content
- What is BJT
- What is FET
- BJT vs FET operation comparison
- Difference Between BJT and FET
- Applications of BJT
- Applications of FET
- Conclusion
- FAQs