BF245 FETs (was: Phaser)

[Rick Jansen]

In message <31E6DCD2 at MSMGATE.M30X.NBG.SCN.DE> you write:
> 
> > Only problem with this circuit is that the FETs specified,
> > BF245C, weren't easy to get really. I could get 2 at one
> > shop, and 4 at another, exhausting both shops' supplies. You
> > cannot substitute BF245A or B, as the A, B, and C denote the
> > pinch-off voltage (A: -0.4..-2.2V,  B: -1.6..-3.8V,  C:
> > -3.2..-7.5V) and drain saturation current. Of course you
> > could choose another FET and adjust the LFO and voltage
> > levels accordingly, but I have no FET equivalents guide.
> 
> I wouldn't mind too much. The "C" types are the ones with
> the highest pinch off voltage. So if you use "A" or "B" types
> you might have to do an overall DC shift on the CV, but
> it should be well within the possible range.

True, but the A and B types are even harder to get. I tried
a few years ago to get some BF245A's, the ones with the low
pinch-off voltage, which are used in the Formant VCO's and
VCF's as buffers. Could not get them. Fortunately as a buffer
a better option was to bend metal-can LF356's a bit and use
them as voltage-buffers. This saved acquiring BF245A's AND
*selecting* suitable Rs with each FET.

Rick Jansen
__
rick at sara.nl   http://www.sara.nl/Rick.Jansen
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