Very accurate analog comparators

Any leads on how to go about building an analog comparator that can detect signals even with 20mV difference?

Hi,

Use a low offset voltage comparator and precision resistors. LM393 has +/-3mV Voffsetmax specification. Maybe you should run a test with it.

Hi,

If you are talking about "IC design" then the thread should be moved to the according section.

In other case:
20mV should be no problem for most comparators.
If you want it more accurate ... just in regards of voltage level ... you should consult a selection guide to find a suitable comparator.
But low overdrive usually means increased switching delay times and high rise/fall times.
If this may cause a problem then consider to use a (fast) Opamp to amplify the signal before you feed the comparator.

But with Opamps another problem may arise: with too high input signal the output of the Opamp may saturate at the supply rail.
Many Opamps suffer from increased delay coming out of saturation. Which sadly increases overalll switching time (and making it non constant: fast when not saturated, slow when saturated. Strange things may happen).
You then should use feedbacked clamping at the Opamp, maybe with fast, low capacitance zeners.
Don't use standard zeners, because they have relatively high capacitance.

Klaus