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[Moved]: Comparator for SAR ADC

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Majid_Vatan_Parast

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Hello everybody

I need to compare zero voltage with a negative voltage , but comparators that are in papers do not work with zero and negative voltages , because their supply voltages are zero and vdd .

How can I find a comparator that has ability to compare zero and negative voltages ??
Please help me
Thanks
 

Re: Comparator for SAR ADC

How can I find a comparator that has ability to compare zero and negative voltages ??
Click to expand...

Let's think about...perhaps making a parametric search ?
 

Re: Comparator for SAR ADC

Hi,

... I agree

but first you need specifications.
* what´s your input voltage range
* any restrictions in switching speed
* switching voltage precision
* what out put voltage
* what output stage? push pull, open collector....
* and everything else that is important for you

I recommend to go through any comparator´s datasheet specifications to find out what is important for you ..

Klaus
 

"Back in the day" +/-10V ADC chip sets used the CMP-05
with +5/-15V supplies, so no problem.

Today the input voltage may be differential (and too, the
rest of the signal lineup until the logic). Then while quantity
is negative, common mode range is still within spec.

You can make level shifting front ends, and you can (with
appropriate technology) make a (mostly) 0-5V design deal
with negative voltages.

For any decent bit-width, the comparison of interest is
trivially negative (what's your input range divided by
2^N?). You only need accuracy about the LSB point,
so maybe (say) -1mV on a 4.096V in, 12 bit ADC. As
long as there's no phase inversion, larger negative
inputs still compare right and accuracy is a don't-care.
 

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