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? 
No it depends on the fet, a fet that is normally off and needs a voltage 
difference to turn it on is known as an "enhancement mode" device, a fet 
that is normally on and needs a voltage difference to turn it off is 
known as "depletion mode".

Afaict most (maybe all) JFETs are depletion mode. Most mosfets are 
enhancement mode but depletion mode ones also exist.

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