Hello Andy and Chris,

Have been following your discussion with interest. I too experienced the "hand grenade effect" of removing the drive whilst using DC coupling. Dave YXM put me right some years ago.

Thanks Andy for the further explanation.

I have always been perplexed by the distortion of the gate pulse that occurs when the drain volts are applied.
This sometimes appears to show up as a slight instability on tail of the drain pulse. Probably of no importance but never heard anyone mention it.

Would appreciate any comments

Mike -GW4HXO
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Subject: Re[2]: LF: Protecting a MOSFET driver chip from MOSFET failure?

Hello Andy,

Monday, August 10, 2015


> No, capacitive coupling with diode restorationends up with near-enough
> the same voltage applied to the gate as you had in thr first place.


> A 0/12v output from the driver chips ends up at -0.7 /+ 11.3 V
> (assuming 0.7V diode drop)




> As for the question of the dual drive with resistors.    The resistors
> may as well say in, just to smooth off edges and reduce dissipation in
> the driver.     i doubt you'll notice any difference.


> Andy  G4JNT

OK, thanks and sorry for the naive questions, lots to learn, I was amused by my friend calling power FET's "Fire Emitting Transistors". I see his point now, they do go with a good bang and sizzle! The wife smelt them downstairs and asked wearily if it meant a longer wait before a job she attached great importance to, but I classed as a boring irrelevance, got done...







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Best regards,
 Chris                            mailto:[email protected]