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mosfets in critical condition

Let me guess... it's NOT normal for a mosfet to register < 40 ohms between D and S with no gate voltage applied...

correct?

Michael

Reply to
mrdarrett
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If the gate is floating it might? Or if it's depletion mode?

Reply to
Jon Slaughter

I've got IRF530 and an IRLZ34N mosfets.

I noticed something was up when my power supply's current limiting circuitry deactivated the power supply.

Debugging: one at a time, I connected the drain to a 12V light bulb, and tapped the gate with +12V. The light bulb turned on, and STAYED on even with the gate voltage removed. That's not supposed to happen, is it?

At first I thought I had a bum IRF530, burned out from previous experiments, so I tried my IRLZ34... same thing...

A TIP31A behaves as I'd expect it to though... turns on, then off when I remove voltage from the base...

Transistor triage...

Michael

Reply to
mrdarrett 

--
Remember that the gate is completely isolated from both the drain and
the source by the gate oxide, so if the charge isn\'t drained the MOSFET
will stay on for quite some time after you disconnect the gate from the
12V supply.

JF
Reply to
John Fields

Oh ok! I'll breadboard a test circuit that grounds the gate, and see if that fixes things...

Thanks,

M
Reply to
mrdarrett

Applied ? Sure there's not some charge on there already.

Now try SHORTING the gate to the source.

Graham

Reply to
Eeyore

Ok, will do when I get home from work.

Mosfets in critical but stable condition...

How's the girl from the pub doing?

Thanks,

M
Reply to
mrdarrett

Will post to the original thread.

Graham

Reply to
Eeyore

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