BJT and JFET transistors

[7@rB]

one of the definition of JFET transistor is that it is preferred for specific applications where BJT cannot be used.
what are these applications?and why bjt cannot be used?

 

[yadavvlsi]

The junction field-effect transistor, or JFET, although over 40 years old, is still solving real-world, small-signal-chain problems typically requiring low power, high impedance, and low noise. They also offer excellent radiation and temperature tolerance, required in many military/high-reliability applications.
**broken link removed**

 

[Cyrus the Great]

hi dear 7@rB .fet has high input impedance compared to bjt .fet has low noise compared to bjt. fet has low power dissipation compared to bjt.Fet has better temp stability as compared to bjt. Bjt is more temp.Bjt has better driving capability (fanout) than fet sensitive than fet and bjt also has has high speed switching compared to fet.
regard
pesarirouni

 

[LvW]

Another area of FET application is the use as a voltage controlled resistor. BJT`s cannot be used for these purposes.

 

[goldsmith]

has low power dissipation compared to bjt

Hi dear all
I don't think it is correct . because the jfet will have a resistor that called Ron ( at saturation ) and thus the dissipation will given by : 1/T integral over Ron*ID^2 dt and about Bjt it will be : 1/T integral over IC * Vcesat dt ( at saturation )
And if you see the aim of creating IGBT s you'll see , because bjt has many benefits e.g thing that i told , that fet or mosfet hasn't , and mosfet or fet , has many benefit that bjt hasn't them , and mixture between them will given IGBT .
One of those reasons , is lower dissipation .
and one other things that we can say is better frequency response of jfets .
Best Wishes
Goldsmith

---------- Post added at 20:04 ---------- Previous post was at 20:03 ----------

BTW : i forgot to say , with jfets , we will be able to design very accurate current sources .