Differential comparator with a dynamic hysteresis

Thread Starter


Joined Dec 14, 2017

I am having great difficulties in a recent project for my university. I have to create and calculate a scheme of a differential comparator with an OP AMP and a dynamic hysteresis |UthH|=±5V with a minimum possible static threshold of the time-domain of the dynamic hysteresis 3*tau=500µs.

I have found this circuit but I am not quite sure if it is correct. Basically AWG1 is the main signal while AWG2 is added noise. Wtih connecting J4 and J5 I add dynamic hysteresis.
Is this the full circuit?
How do I calculate the elements to fulfill the 3*tau=500µs requirement?
How do I fulfill the |UthH|=±5V requirement?
What should I look for in the datasheet while choosing an op-amp?
I would greatly appreciate any help on this matter.

Best regards


Joined Sep 16, 2012
If this is homework of some sort, have you tried asking your professor for help?
Have you tried building the circuit? Building circuits answers many questions. And it looks like your circuit is designed to educate. I would not connect J1 until you understand what is going on with the rest of the circuitry.
I'm not sure what you mean by UthH.
Generally speaking, you do not want to use an opamp in comparator circuits. The 311 is a an older part, but works well for learning. I've used it before. You have to know all of your requirements before selecting a part. The LT1017 or LT1018 are also good general purpose comparators

Many micros have comparators in them these days where the reference voltage can be adjusted on the fly.