A transistor is basically a three-terminal semiconductor device used for controlling, amplifying and generating electric signals. It is the appropriate configuration of numerous semiconductor materials.
Silicon, germanium and gallium-arsenide are common semiconductor materials used by transistors.
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A transistor requires low power for their operation and low power dissipation as they are small in size. It makes the transistor usable in various applications including amplifiers, switching circuits, oscillators and virtually in almost any electrical circuit.
There are too many types of transistors, each of which differs in its features and each has its own advantages and drawbacks. Bipolar junction transistors (BJTS) and field-effect transistors (FETs) are two different types of transistors and may be found in electrical and electronic circuits as switches and amplifiers.
Differences between BJT and FET transistors
Bipolar Junction Transistor (BJT)
Junction transistor is generally called as Bipolar Junction Transistor (BJT).
Bipolar junction transistors are bipolar devices. The operations in this transistor depend on the flow of both majority and minority current carriers.
BJT suffers from storage effects of minority carrier. Thus, it has a lower switching speed, and higher cut off frequencies.
The bipolar junction transistors are regulated by the current. The BJT controls the output current with the base current.
The bipolar junction transistor comprised of three terminals, which are the emitter, the base and the collector. Such terminals are referred to as E, B and C
The BJT transistors have low impedance inputs, and this allows high current to pass through the transistor. The input circuit of the BJT is forward-biased. So BJT has very small input impedance.
In this type of transistors, the offset voltage is required.
The power consumption of BJT is more than FETs transistors.
BJT has lesser thermal stability than FET due to the positive temperature coefficient at high current levels, which leads to thermal breakdown.
BJTs are applicable for low current applications.
FET (Field Effect Transistor)
The Field-Effect-Transistor (FET) is another transistors type.
Field-effect transistors are unipolar devices. In FETs transistors, the operations depend only on the flow of majority charge carrier.
As compared to BJTs, the FETs transistors do not suffer from storage effects of minority carrier. Thus, it has a higher switching speed and cut off frequencies.
Field-effect transistors are regulated by voltage. In FETs, the output current is regulated by the Gate voltage.
The field-effect transistor consists of three terminals, namely source, drain and gate. These terminals are denoted by S, D and G.
FETs have high input impedance compared to BJT transistors. The input circuit of FETs is reverse biased. Thus FETs experiences significantly higher input impedance and lower impedance from the output. FETs functions as a buffer amplifier because they provide a large degree of separation between input and output.
In this type of transistors, there is no requirement of the offset voltage.
The power consumption is less than BJTs.
FETs have more thermal stability due to a negative temperature coefficient at high current levels and prevents it from thermal breakdown issue.
FETS are applicable for low voltage applications.