[sdiy] On the CD4007 switch thing

[Barry Klein]

I may be mistaken but I seem to remember a fet to ground driven by an
inverter from the part, a series fet to the "-" input, and a fet in the
feedback loop somehow.  The fet in the feedback loop was to improve
linearity due to distortion of the series input fet.  It was kinda trick
so it stuck in my mind.  I think I had the circuit in an old pc that I
tossed, thinking there were no important files on it....  arrrghhhh.
What happened to "Electronics" magazine I wonder.  Did it turn into EDN?


-----Original Message-----
From: René Schmitz [mailto:uzs159 at uni-bonn.de] 
Sent: Wednesday, January 06, 2010 3:13 PM
To: Barry Klein
Cc: Synth-DIY
Subject: Re: [sdiy] On the CD4007 switch thing

Hi Barry,

Even though I don't have those articles, I think I know how this thing 
might look like. On my site you can see a switch arrangement 
(misc->signal switch) that allows full +-15V swings to be processed with 
a standard CMOS switch. Just use the switch in a "current to virtual 
ground" configuration, and prevent that it ever sees "high" voltages. 
(protection diodes keep the swing below 600mV or so when the switch is 
open). Note that the switches are powered from 5V, but the opamps are 
run off +-15V.

Now a 4007 can emulate a 4016 type switch. Have a look at the 4016 
datasheet to see how. http://www.fairchildsemi.com/ds/CD%2FCD4016BC.pdf
The inverter pair is there, and you have 4 transistors left to build two 
switches with. So either spdt or dpst are possible.

Hope that helps.

Happy New Year,
  René

Barry Klein schrieb:
> Any of you in Australia have this in your garage?:
> Electronics Australia 
> Dec 7 1979 Wien bridge selects notch filter bandwidth
> 
> This may be the same issue as Dec 7 1978 here in the states....
> This is the first Design note of the bunch.
> 
> Barry
> 
> 
> 
> 
> 
> 
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