[sdiy] FET for VCO cap discharge

[Magnus Danielson]

From: ASSI <Stromeko at compuserve.de>
Subject: Re: [sdiy] FET for VCO cap discharge
Date: Mon, 24 Oct 2005 23:10:00 +0200
Message-ID: <200510242310.00449.Stromeko at Compuserve.DE>

Hi Achim,

> On Montag, 24. Oktober 2005 02:13, harrybissell wrote:
> > Whats more... don't ~most~ of them have an intrinsic reverse diode
> > across the drain-source... ???
> 
> All power MOSFETS have that diode, it is a direct result of their 
> construction (bulk and source are connected internally).

Yes, but as far as I can see, in a normal VCO setup, you would not really
end up in a reverse biasing situation of drain-source. Unless ofcourse that
the pull of the gate capacitance would move the virual ground too much.

As far as I can see, the gate capacitance and the effects of pulling it is so
far the only obsticle I can see when doing just minor changes to the scheme.

> > (I know some don't, but I think they are uncommon. A diode in series
> > can block the reverse, but that kind of defeats the purpose...)
> 
> Those still have the diode, but the manufacturer does not want you to 
> use it to freewheel any inductive loads.

Hmm... don't use this feature... ;O)

Cheers,
Magnus