[sdiy] Auto Center waveforms

[Eric Brombaugh]

Sounds wonderfully complex. What's wrong with a DC blocking cap?

Eric

On Jul 14, 2009, at 6:45 AM, Jerry Gray-Eskue wrote:

>
> I have been thinking about centering arbitrary wave shapes on 0 volts.
>
> Wave shapers and some VCO waveforms tend to create waveforms with a dc
> offset and it would be nice to have a circuit that would "balance"  
> these so
> that the sum of the + voltage = the sum of the - voltage.
>
> To do this it would seem that if you took the sum of one waveform  
> cycle
> using a simple integrator you would have a voltage that represents  
> the DC
> offset. Using the proper scaling you could then subtract this  
> voltage from
> the waveform to remove the offset. A pair of voltage hold circuits  
> would
> store the voltage of the previous cycle and remove the offset from the
> current cycle. The integrator (s) would reset each cycle after the  
> voltage
> hold circuits were updated.
>
> The problem that I am having with this scheme is that it appears the  
> period
> of the waveform must be used to scale the resulting voltage. Now it is
> simple enough to use a constant current into a second integrator to  
> derive a
> voltage representing the time period, and it would appear that using  
> this
> voltage and a multiplier in the feed back of an op amp will allow  
> division
> of the total voltage / period voltage.
>
> The issue with this approach is cost and complexity. It seems like  
> there may
> be a "Slick" way to do this without resorting to expensive ICs and  
> still
> give good offset removal performance.
>
> Any thoughts, or ideas on a better method ?
>
> - Jerry
>
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