Fast analog sw. as VC resistor

[Tim Cockram]

Hi Mark

You have got the math right in your post.

Using Analog switches as Pots/ Attenuators is quite common. A US company called Innovonics use
this in  broadcast processors and Studer (very expensive and good quality) use this technique for an out 
put limiter in at least one of their desks.  In the synth world Roland effectively used this technique to 
control the ADSR settings on the JP4.

Think also switched capacitor filters eg the MF10.

You do have to take care to ensure that the garbage generated by the oscillator doesn't get in to the 
rest of the circuitry (this includes filtering the output of the device!!!) and that the signal that you are 
working on falls within the power supply range of the switch (4016/66 run quite nicely on +/- 7v5 or 
you could use the more expensive DG or SSM series which have much greater).

Regards  

Tim

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Tim Cockram
E-mail: tim at redragon.demon.co.uk 

Phone:-UK-1222-384041
Fax:-    UK-1222-390326


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