Re: Strange Mosfet Results

From: colin (no.spam.for.me_at_ntlworld.com)
Date: 08/03/04 

Date: Tue, 03 Aug 2004 09:22:39 GMT

"Active8" <reply2group@ndbbm.net> wrote in message
news:1pk4g0hjm1g7a.dlg@news.individual.net...
> On Tue, 3 Aug 2004 03:03:34 -0400, Activ8 wrote:
>
> >>
> >> Vgs(th)/Vcc = exp(-2/(R*C))
> > ^^^^^^^^^^^^^^
> > Yup. Use it. It'll work.
> >>
> >> so
> >>
> >> R*C = -2/ln(Vgs(th)/Vcc)
> >>
> >> For a Vgs(th) of 4V, and a Vcc of 4V, you have
> >>
> >> R*C = -2/ln(4/5) = 9
> >>
>
> BTW, John mentioned that the diodes blocked the discharge.
>
> |
> ||-+
> ___ ||<-
> -|___|------+-------||-+
> | |
> |
> ---
> ---
> |
> |
> ===
> GND
>
>
> That'll work, too, and the same equation applies. Just don't let
> Vcc/R exceed the maximum sink current of the SRs.
>
> --
> Best Regards,
> Mike

rather than conect the capacitor to ground u cld make use of the miller
efect and conect it from gate to drain. this wld make any delay much more
related to diming rather then delay before starting to turn off. basicaly
the miler efect multiplies the efective capacitance by the gain of the
circuit, wich is probably 30 or more at a very wild gues, its basicaly gm x
r load. wich both vary with curent.

Colin =^.^=

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