Hi all. I'm designing a simple HV shunt regulator at the moment (for a tube stage) and am prevented from using lateral fets because their highest Vds seems to be 200v or so.
Also I'll be only running them at a few mA, so they will be have a negative Vgs tempco anyway.
So the plan is to use vertical fets.
Now I gather the DC feedback will take care of the Vgs decrease with temperature, but I
am worried about the phenomenon of thermal "hot spots" in VFets
Are there any tips to operate VFets safely in these conditions? Apologies if this is a silly question, as I know Nelson Pass's stuff has no problem on this front....
Apologies if this is in the wrong forum, I just thought this would be the place to ask
Cheers dudes
Also I'll be only running them at a few mA, so they will be have a negative Vgs tempco anyway.
So the plan is to use vertical fets.
Now I gather the DC feedback will take care of the Vgs decrease with temperature, but I
am worried about the phenomenon of thermal "hot spots" in VFets
Are there any tips to operate VFets safely in these conditions? Apologies if this is a silly question, as I know Nelson Pass's stuff has no problem on this front....
Apologies if this is in the wrong forum, I just thought this would be the place to ask
Cheers dudes
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wildswan said:Hi all. I'm designing a simple HV shunt regulator at the moment (for a tube stage) and am prevented from using lateral fets because their highest Vds seems to be 200v or so.
Also I'll be only running them at a few mA, so they will be have a negative Vgs tempco anyway.
So the plan is to use vertical fets.
Now I gather the DC feedback will take care of the Vgs decrease with temperature, but I
am worried about the phenomenon of thermal "hot spots" in VFets
Are there any tips to operate VFets safely in these conditions? Apologies if this is a silly question, as I know Nelson Pass's stuff has no problem on this front....
Apologies if this is in the wrong forum, I just thought this would be the place to ask
Cheers dudes
I have used vertical power MOSFETs as pass regulators in a tube amplifier with no problem (screen voltage regulators in a Pentode amplifier with KT88s, and also for driver and input stage B+).
Hot spots should be no problem in your application as long as you stay below rated dissipation and do a decent job of heat sinking them.
Cheers,
Bob
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