I thought about this a little more. The Vgs specs in the data sheet must be the maximum allowed before blowing up the gate insulation. A lot of the ones I looked at had Vgs around +/- 20, or sometimes +/-40 volts. Maybe in my design, since the drive voltage is over the max, I can simply use resistor dividers to get the gate voltage to a reasonable level. It may change the turn on time though.
----- Original Message -----
From: gene glick
Date: Sunday, December 3, 2006 5:45 am
Subject: gEDA-user: mosfet design help
To: gEDA user mailing list
> I want to build a mosfet inverter that also translates voltages.
> Pretty
> much standard mosfet inverter, nmos is lower transistor, pmos is
> upper
> transistor. The upper pmosfet Vsource is +5VDC, and mosfet
> Vsource is
> -5VDC. But, the gate voltage is +/- 50VDC.
>
> Although the gate voltage exceeds the turn-on threshold of the
> mosfet's
> - but does it violate any max values for Vgs or Vgd? At these
> levels,
> the Vgs is going to around 55 volts. The Vds is fine, and is
> easy to
> select a transistor for these levels.
>
> It's not clear to me what the Vgs and Vgd maximums are, from
> reading
> various mosfet data sheets. Any help?
>
> gene
>
>
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