[sdiy] VCR - Voltage Controlled Resistor

[harrybissell]

Hello Scott (et al)

You are now getting there. The FET distortion is why they are seldom used.  If
you add
the linearizing resistors, the impedance drops a lot.

Usually the more successful FET designs use them in shunt mode... with a fixed
series
component and a linearized FET to ground. Most FET phasers do this. Guitar waves
have
very low amplitude after a huge peak... the distortion will be very short and no
one will be
the wiser. VCO waves are constant amplitude.

I suggest you hie hither to Osamu Hoshuyama's site. He has some ideas there on
FET linearization
iirc.  One of them is truly a new idea that has not been commonly used !

Now take two VAC-TROLLS and call me in the morning   :^P

H^) harry

Scott Gravenhorst wrote:

> Ok, well I still have the H11F1 option, I've got a couple here that I can
> use, but I will first try to get the best I can out of a 4007, since I really
> would like to see that work if it can.  The H11F1 also eliminates the need
> for a bastardized ground/powersupply thing, but the large signal spec seems
> to suck for that one too, the V-I curve is linear only from about -50 mV to
> +50 mV.
>
> I was hoping to be able to drive the filter with around 3 volts of input, but
> it's not looking good for that.  Perhaps this is why the WASP uses an OTA...
>
> "Theo" <t.hogers at home.nl> wrote:
> >I experimented a bit with those but found other FET like the BF245 behave
> >too similar to the special VCR FET to jump even half a inch.
> >
> >Could not find the home of Siliconix the gallier but he lives in Vishay now,
> >thanks for the tip.
> >The FET as VCR application note AN105 should be at the Vishay website.
> >
> >Theo
> >
> >----- Original Message -----
> >From: Magnus Danielson <cfmd at bredband.net>
> >To: <synth-diy at dropmix.xs4all.nl>
> >Sent: Sunday, July 18, 2004 3:41 AM
> >Subject: [sdiy] VCR - Voltage Controlled Resistor
> >
> >
> >> Hi!
> >>
> >> There should be folks enjoying this!
> >>
> >> Vishay Siliconix has Voltage Controlled Resistors in their productrange.
> >> Their VCR2N, VCR3N and VCR7N does this. They dynamics may not be much to
> >jump
> >> high for, but at least something.
> >>
> >> Cheers,
> >> Magnus
> >
>
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