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Difference between bipolar junction transistor (BJT) & field effect transistor (FET)


The Difference between bjt and fet

                           BJT                                  FET
1:BJT (bipolar junction transistor ) is the bipolar device. 1:FET (field effect transistor) is a uni junction transistor.
2:Its operation depends on both majority charge carriers and minority charge carriers. 2:Its operation depends on majority charge carriers which may be holes or electrons.
3:Input impedance of bjt is very less i.e (1k -3k) 3:Input impedance of FET is very large.
4:It is the current control device. 4:It is the voltage controlled device.
5:It is more noisy. 5:It is less noisy.
6:Its frequency variations effect its performance. 6:It has high frequency response.
7:It is temperature dependent device. 7:It has better heat stability.
8:It is cheaper. 8:It is costly than bjt.
9:It is bigger in size than FET. 9:It is smaller in size than BJT.
10:It has an offset voltage. 10:It has no offset voltage.
11:It has more gain. 11:It has less gain.
12:It has high output impedance because of high gain. 12:It has low output impedance because of less gain.
13:Its collector and base are more positive than emitter. 13:Its Drain is positive,gate is negative w.r.t to source.
14:Its base is negative w.r.t to emitter. 14:Its gate is more negative w.r.t to source.
15:Bjt has three parts ( base ,Emitter and Collector). 15:Fet has three parts (Drain,Source and Gate).
16:It has high voltage gain. 16:It has low voltage gain.
17:It has low current gain. 17:It has high current gain.
18:Its switching time is medium. 18:Its switching time is fast.
19:It is easily biased.  19:Its biasing is difficult.
20:These are preferred for low current applications. 20:These are preferred for low voltage applications.
21:It requires small amount of current to keep on. 21:They requires small amount of voltage to keep on.

22:It consumes more power.

23:It has negative temperature co efficient.

22:It consumes less power.

23 :It has positive temperature co efficient.


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