How to guarantee that a comparator does not enter the linear region of operation

Hello David,

A comparator should not go into a "linear" range. THe output stage is a logic output and only has two states. An op-amp used as a comparator can go into a linear range.

There is no "minimum" detectable voltage. The output will change as soon as the input voltage crosses the reference voltage (plus internal offset).

However, the output can start to "chatter" as the two inputs start to come within 100's of microvolts of each other due to triggering on the inherent noise of the comparator and input signals.

To prevent this, hysteresis can be added to prevent the chatter.

Please see the TI precision labs section on Comparators, particularly section 2.

 TI Precision Labs - Comparators (4)

And also see the following appnotes:

 Comparator with and without hysteresis circuit (Rev. A)
 Non-inverting comparator with hysteresis circuit (Rev. A)
 Inverting comparator with hysteresis circuit (Rev. A)

Some comparators, such as the TLV7021 series, has a few mV's of built-in hysteresis.