[sdiy] CMOS V.C.R. with 1V/Oct Response

[Scott Gravenhorst]

Yes, that looks nice.  I have a question:  If I wanted to use
a linear CV, could I replace the expo converter (sink?) with a 
linear one?  (sure...)  but the real question is would doing so 
extend the usable linear range?

Also, would there be a problem with using this approach with
VCRs that have Vss connected to a virtual ground instead of 
real ground?  (I am guessing this would work)...

Grant Richter <grichter at asapnet.net> wrote:
>Groovy!
>
>What a great design! Nice job Mike!
>
>One question that springs to mind is the signal levels. Will the resistors
>tolerate swings below Vss? Or does the signal voltage have to remain above
>Vss?
>
>Electronotes #81 Page 8 has an article "A Design for a New Multi-Mode
>Voltage Controlled Filter" (the so-called "Dual Shift" filter) which shows
>implementing the equivalent of a state variable using all-pass sections. The
>all-pass sections are controlled by variable resistors to ground. This would
>seem to be an ideal application for this control circuit.
>
>Also the general design of an all-pass network is much simplified by this
>control design. I suspect only one Master FET would be needed, even
>uncompensated 4049s should track well enough for a phase shifter. That would
>require only 3 x 4049s to make a 16 pole phase shifter.
>
>> From: eq927 at freenet.carleton.ca
>> Date: Fri, 03 May 2002 20:04:00 -0400
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: [sdiy] CMOS V.C.R. with 1V/Oct Response
>> 
>> Hello List,
>> Osamu Hoshuyama kindly provided webspace for a schematic of a circuit I
>> built earlier this year. It is a design for a multiple
>> CMOS voltage-controlled resistor where the resistance is constrained to
>> be an exponential function of the applied control voltage. The schematic
>> is here:
>> 
>> http://www5b.biglobe.ne.jp/~houshu/synth/mike_irwin/cmos-vcr.gif
>> 
>> Regards, Mike
>> 
>

=========================================================  
- Government: The other religion.
- The media's credibility should always be questioned.
- Lambs who lie down with lions are lunch.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.GTE.NET/res0658s/FatMan/
-- NonFatMan: home1.GTE.NET/res0658s/electronics/