among JFET & EMOSFET & DMOSFET which has high input impedence

[Srikanth Yadav]

among JFET & EMOSFET & DMOSFET which has high input impedence & how explain the reasons

 

[mathespbe]

JFET use PN junction to provide high input impedance.

MOSFET use isolated gate to provide high input impedance...

Due to PN junction in JFET the leakage current lead to reduce the I/P impedance... Hence MOSFET has higher I/P impedance than JFET.
DMOSFET and EMOSFET has almost equally higher I/P impedance...

I guess due to the depletion channel the DMOSFET has slightly lower I/P impedance than DMOSFET...

the I/P impedance comparision would be JFET << DMOSFET << EMOSFET...

If i'm wrong correct me...

 

[dick_freebird]

Do you care more about DC leakage, or about AC impedance
@ frequency? And what is your signal swing you will impose,
while looking to have that high-Z (and possibly constant-Z)
attribute?

AC impedance is going to follow things like current rating
or on resistance. There are tradeoffs there that don't have
specifically to do with device type vs device type. Other
than that you're bloody unlikely to find a 100A JFET
anywhere.