[sdiy] voltage ladder with hysteresis

[David Brown]

I'm not exactly sure of the application.  Some of this dither will be 
due to noise on the inputs to the comparators.  Since this is a 
sequencer, your frequency is probably low. Noise is broadband so you 
can reduce the noise by rolling off the frequency of your input 
stage.  For my CVS sequencer, I rolled it off at 150 Hz and it made a 
big difference.  I can't suggest a frequency since I don't fully 
understand the application but you might try this and see what impact it has.

I tried hysteresis in my comparator on my quantizer module to reduce 
dither and had a heck of a time keeping the inputs referenced 
correctly so 0 volts would quantize to 0.  I think they are all off a 
bit as you suggest.

Dave


At 10:07 PM 5/12/2007, mark verbos wrote:
>Hi there,
>
>I built a ladder of 16 comparators on a sequencer. The CV goes
>through and inverting stage and thresholds are set with a string of
>resistors from ground to -15 volts, going to the non-inverting input.
>I found the transition points were blurry, and it needed some
>hysteresis. I added 1M resistors from the comparator outputs to the +
>inputs and this works fine on the lower stages, but I find that when
>I sweep the input with a saw wave, now the lower stages go slow and
>it moves faster as it goes to the right. All the way on the highest
>stages wouldn't even switch right until I upped the feedback resistor
>to 2M. Is there some standard way to figure this problem out?  Should
>I just put a 1M on stage 1 and a 2M on stage 16 and divide equally
>between?
>
>
>hmmm..
>
>Mark
>
>
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