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Fast Rail to Rail CMOS comparator without clocks

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viperpaki007

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Hi,

I am trying to design fast rail to rail CMOS comparator with out clock signal. Can anybody refer some circuit.

regards
 

Hi,

why designing your own?
why not using ready to buy?

many manufacturers have such comparators.

Klaus
 

iIam designing an integrated comparator for custom IC design. Comparator will be part of a big integrated circuit. Therefore, i cannot use comparator from some manufacturer.
 

Hi erikl,

This circuit that you have referenced is a generic one? Is the most common fast comparator?

There is any other topology that doesn't need a pre-amplifier?

Regards.
 

The comparator is a bridge between analog and digital circuit so it need preamplifier to prepare signal for digital backend of circuit.
 

Hi Dominik,

Thanks. However, maybe I have questioned in a wrong way.

What I meant to ask was if there is any architecture where the pre-amplifier is part of the positive feedback circuit, that is, instead of having the differential pair as a first stage, lets say, and then the positive fdbck as a second, can we have that positive feedback for example as a load for the differential pair?

If it is possible, what's the nome of such circuit?

In my case the fast comparator is to be used to compare a sawtooth wave with a reference that will vary very slowly.

Hope made myself more clear.

Thanks in advance.
 

Positive feedback used for hysteresis. this is the % of output swing and ratio of feedback resistors to the midpoint of swing. This is how Schmitt trigger inputs are made, ranging from 1% for small and 30% for common CMOS gates.

Avalanche switching diodes are even faster. But normally you only use hysteresis to prevent glitches from input noise near threshold, not increase slew rate of output.
 

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