The Source terminal in FET is analogous to the Emitter in BJT, while Gate is analogous to Base and Drain to Collector. The three terminals of FET are Gate, Source and Drain. Though FET is a three terminal device, they are not the same as BJT terminals.
Gain is characterized by transconductanceįET is used in circuits to reduce the loading effect.įETs are used in many circuits such as Buffer Amplifier, Phase shift Oscillators and Voltmeters. Let us try to summarize the advantages of FET over BJT. To prefer a FET over BJT, there should be few advantages of using FETs, rather than BJTs. Transconductance is the ratio of change in output current to the change in input voltage. Gain is characterized as transconductance.
Noise is low − There are no junctions present in the conduction path. Voltage controlled device − As the output voltage of a FET is controlled by the gate input voltage, FET is called as the voltage controlled device. High input impedance − The input current in a FET flows due to the reverse bias. Unipolar − It is unipolar as either holes or electrons are responsible for conduction. The following are the varied features of a Field Effect Transistor. Hence the current conduction of a FET is done by either electrons or holes. The FET is a unipolar device, which means that it is made using either p-type or n-type material as main substrate. The following image shows how a practical FET looks like. It has many advantages like low power consumption, low heat dissipation and FETs are highly efficient devices. The main advantage of FET is that it has a very high input impedance, which is in the order of Mega Ohms. It is a voltage controlled device unlike a bipolar junction transistor. Field Effect TransistorĪn FET is a three-terminal unipolar semiconductor device. The functionality, configurations and applications are all the same. A normal transistor which we had discussed in the previous chapters come under this category. The PNP transistor is made by placing an ntype material between two p-type materials.īJT is a current controlled device. The NPN transistor is made by placing a ptype material between two n-type materials. The types of BJT are NPN and PNP transistors. The following image shows how a practical BJT looks like. Usually NPN transistor is preferred for the sake of convenience. It has got two types of configurations NPN and PNP. This BJT is nothing but a normal transistor. Bipolar Junction TransistorĪ Bipolar junction transistor, shortly termed as BJT is called so as it has two PN junctions for its function. The primary transistor is the BJT and FET is the modern version of transistor. Each transistor is specialized in its application. There are many types of transistors in use.
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