28 May 2018

Difference between JFET and BJT

One of the major differences between JFET and BJT is that JFET is a unipolar device while BJT is a bipolar device. Here this article gives information about the difference between JFET and BJT to know more details about it.

Difference between JFET And BJT:

  • The JFET stands for junction field-effect transistor while BJT stands for the bipolar field-effect transistor.
  • JFET is a unipolar device, and BJT is a bipolar device.
  • JFET is the low noise level, BJT is the high noise level.
  • Booth JEFT and BJT are three-terminal devices. JEFT has three  terminals gate, drain, and source, BJT has three terminals, base, emitter, and collector
  • In JFET the operation depends on the control of a junction depletion under reverse bias while in BJT the operation depends on the injection of minority carrier across the forward bias junction.
  • JFET voltage control device while BJT is a current control device.
  • JFET is easily damaged by static, but BJT is robust.
  • JFET has better thermal stability but  BJT is less thermal stability.
  • JFET is a high input impedance, and BJT is a medium input impedance.
  • JFET has a high current gain device, and BJT has a low current gain device.
  • JFET has a low voltage gain device whereas BJT has a high voltage gain device.
  • JFET has a high output impedance, and BJT has a low output impedance.
  • JFET has a fast switching time whereas we talk about BJT, which has a medium switching time.
  • JFET is difficult to bias but BJT is easy to bias.
  • JFET is more expensive compared to BJT.
  • JFET is less noisy while BJT is much more noisy than FET.
  • JFET is a high-frequency response but in BJT frequency variation affects the performance.
  • Gain is characterized by trance-conductance using JFET, in BJT is characterized by voltage gain.
  • JFET has a small gain-bandwidth product while in BJT bandwidth is greater than FET.
  • JFET has no offset voltage, so it works better as a switch or chopper, BJT has always an offset voltage before switching.
  • BJT is bigger than FET.
  • JFET is preferred to the low voltage applications whereas BJT is preferred to low current applications.
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