Andre Abelian wrote:
> Hi to all,
>
> Based on my understanding bipolar transistors pnp or npn they are
> normally off until apply voltage to the base to turn it on but FET
> transistors are opposite they are normally on until apply power to the
> Gate and Source to turn it off. My question is: Are all FET, JFET,
> MOSFET and etc FET transistors work the way I described above or I
> misunderstood? 
>
>
> Any feedback will appreciate.
>
> Thanks
>
> Andre
>
>   
Nope, you misunderstood.

As I understand it, and I am new myself, Transistors are mostly current 
based.... you apply a current x to the base to get a proportionately 
larger current Bx through the collector.
FET's are more voltage controlled... but, it depends on the 'doping' of 
the FET as to whether they are normally on or not.... This is what makes 
JFETS, and MOSFETS different. Further, JFets are always 'depletion' mode 
devices, wheras MOSFETS could be depletion or enhancement modes, but you 
only get N-Channel Depletion mode MOSFETS, thus, there are effectively 5 
types of FET, N JFET, P JFET, Depletion NMOSFET, and Enhancement N and P 
MOSFETS.

With some of them they conduct when the gate is grounded, with others 
they do not...

You really need to read up on them all to get it all straight.


Rolf
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