Electronics - Field Effect Transistors (FET) - Discussion


What is the input impedance of a common-gate configured JFET?

[A]. very low
[B]. low
[C]. high
[D]. very high

Answer: Option A


No answer description available for this question.

Arbind Kumar said: (Sep 16, 2011)  
Answer explanation please.

Siva said: (May 14, 2013)  
Common gate JFET has low input impedance and high output impedance.

Sumit Choubey said: (Jul 17, 2013)  
Common gate FET always has high input impedance.

Aishwarye said: (Aug 27, 2013)  
Common gate FET always has high input impedance.

Shivani said: (Dec 31, 2013)  
What high input impedance make difference ?

Shivank Dixit said: (Sep 25, 2014)  
How input impedance of common gate FET is low?

Sindhu said: (Oct 14, 2014)  
Input impedance of FET is always high.

Asha Rani Pattedar said: (Apr 10, 2015)  
For common source & common drain the input current Ii=0. So input impedance infinite, where as in common gate input current is -Id so input impedance is very low.

Abhishek said: (Oct 11, 2015)  
Why input impedance is high?

Essilfie Ishmael said: (Feb 24, 2016)  
JFET has high impedance rather since it is always reverse bias. If it were to be forward bias then it will have low impedance.

Divya said: (Apr 9, 2016)  
Just like a bit CB mode, here common gate JFET concept, the input signal applied to the source, the output is taken at the drain, and the source is grounded.
Therefore, it is having less input impedance, used as a voltage follower.

Vipin said: (Dec 16, 2016)  
Right @Divya.

Nagi said: (Jan 11, 2017)  
Well said, you are right @Divya.

Uday Kumar said: (Jan 28, 2017)  
Good answer @Divya.

Ankit said: (Feb 19, 2017)  
Input impedance of JFET is always very very because a reverse voltage V(GS) is applied across the gate and source.

Emmanuel Ekirapa said: (Mar 22, 2019)  
Common drain and source impedance is high depending on the small adjustment in the gate source voltage thus common gate configuration inputting a very low impedance and high out put impedance. Therefore, the answer is very low.

Nishi said: (Jun 22, 2020)  
Yes, you are right @Divya.

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