Depletion-mode P-channel MOSFET

Can a JFET be used? They are depletion mode, commonly.

Sometimes yes, but they don't like bipolar gate voltages and their VDS_MAX is usually much smaller than that of a MOSFET. Is there any physical reason not to produce them or is it just marketing/sales? The mankind used to produce all sort of weird semiconductor devices, UJT and tunnel diodes leading the way, but not this kind of a MOSFET. Not sure why.

Best regards, Piotr

Only "several", not thousands or millions? :-)

Pch sucks in general anyway, then add to that the rarity of depletion. You might as well ask for a Pch JFET (which amazingly still exist at all: you have your choice of J271, J176, MMBF5462 and their sisters).

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

They're used sometimes in ICs, I believe, but a depletion PFET is a bit of a niche part, mostly useful with high voltage negative supplies. You can get 40V P-JFETs, but that's about the closest thing out there.

Cheers

Phil Hobbs

Several is still considerably more than the number of sane UJT applications. ;-P

Use them and love them. They fit nicely e.g. in the passive MOSFET gate discharge circuits. JFETs also have the unique capability of morphing drain into source in response to the applied gate voltage, sometimes very useful. :-)

Best regards, Piotr

Also super useful in polarity protection circuits for low voltage.

Cheers

Phil Hobbs