[sdiy] FET for VCO cap discharge

[Magnus Danielson]

From: "JH." <jhaible at debitel.net>
Subject: [sdiy] FET for VCO cap discharge
Date: Sat, 22 Oct 2005 15:55:52 +0200
Message-ID: <000501c5d710$53154a80$0200a8c0 at jhsilent>

Hi Jürgen,

> Here's something I want to share with you.

> This is quite a demand on the discharge transistor, considering I wanted 
> a JFET.
> 
> I found that the 2N4391 is not good enough for this. (It's great for
> 1nF, but for larger caps, I'd have to increase the discharge time,
> which I didn't want.)
> 
> So I started paralleling devices. This works. But I also found a
> quite common JFET that is better than the 2N4391 in this
> application: the BF256C.
> Two BF256's in parallel were enough to discharge 10nF in
> Ian's circuit in ca. 500ns. I put in 3 in parallel just to be sure.
> 
> So I thought I'd pass this on - the good old unexpensive BF256C
> may be a very good choice in that kind of oscillators.

Mmmm, that was good news to hear! Really! I have been somewhat concerned about
the state of things, availability etc.

So, thanks for taking the effort and doing some experimentation and sharing it
with us!

Cheers,
Magnus