Explain the fundamental difference between BJT and FET. Illustrate the operation of n-channel and p-channel FET and draw biasing circuits and Drain current (ID) vs Gate-to-Source (VGS).
Answers
Explanation:
Bipolar junction transistors are bipolar devices, in this transistor there is a flow of both majority & minority charge carriers.
Field effect transistors are unipolar devices, in this transistor there are only the majority charge carriers flows.
Bipolar junction transistors are current controlled.
Field effect transistors are voltage controlled.
In many applications FETs are used than bipolar junction transistors.
Bipolar junction transistor consist of three terminals namely emitter, base and collector. These terminals are denoted by E, B and C.
Field effect transistor consist of three terminals namely source, drain and gate. These terminals are denoted by S, D and G.
The input impedance of field effect transistors has high compared with bipolar junction transistors.
A BJT needs a small amount of current to switch on the transistor.The heat dissipated on bipolar stops the total number of transistors that can be fabricated on the chip.
Whenever the ‘G’ terminal of the FET transistor has been charged, no more current is required to keep the transistor ON.
The BJT is responsible for overheating due to a negative temperature co-efficient.
FET has a +Ve temperature coefficient for stopping over heating.
BJTs are applicable for low current applications.
FETS are applicable for low voltage applications.
FETs have low to medium gain.
BJTs have a higher max frequency and a higher cutoff frequency