[sdiy] voltage ladder with hysteresis

[mark verbos]

Basically, I'm building an A to D converter. So, similar to your  
quantizer.


Mark




On May 13, 2007, at 1:35 AM, David Brown wrote:

> 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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