Osc reset time

[Tony Clark]

> Thinking about using analogue switches to reset the cap in a saw wave core,
> it occurs to me that it should be possible to use analogue switches so that
> the capacitor does not need to be discharged to be 'reset'.
>  
> If you have a dual two-way analogue switch, with very low on resistance, you
> could connect the capacitor so that you can reverse its polarity in the
> circuit - ie a comparator detects the peak level and toggles the switches so
> that the connections from the cap to the ref voltage and the current source
> are swapped. At the next peak, they are swapped back. This should give near
> instant reset times.

   This is pretty much the principle of voltage inverter chips.  I 
imagine that what you'd have would be a symmetrical sawtooth on the 
output.  Whether or not that would be any "faster", I haven't a clue.

> I would expect this has been done before if it's workable.
> Is this likely to have any advantage over discharging the cap ?

   Well just symmetrical waveform output, if that's what happens.  That 
would be a plus, actually, as at high frequencies I notice uneven 
waveform distortion.  So perhaps having a symmetrical integrator would 
maintain better waveform integrity at higher frequencies?
   Disadvantage?  More suppy noise, I'd hazard a guess.  My experiences 
with voltage inverters are that they are fairly noisy.

   Tony

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I can't drive (my Moog) 55!         |     The E-Music DIY Archive
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