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How to modify hysteresis of cross coupled comparator

rati89

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Hi

I want to design a comparator with varying hysteresis. What are the important parameters that should be considered while setting hysteresis? How can the hysteresis be modified?

Thanks
Rati
 

wwfeldman

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this explains how hysteresis works and why it is used
while the discussion uses specific devices, the ideas apply to any comparator

https://www.maximintegrated.com/en/app-notes/index.mvp/id/3616

i'm an old fan of national semiconductor application notes
i have always found them useful
(these days they are hidden behind ti)

http://www.mpu51.com/mcucity/appnote/AN-074_LM339 application note.pdf

you can change the hysteresis by changing the value of the positive feedback resistor
one way to do that is to put a FET across the resistor
as you turn the FET on through its linear region, the net resistance decreases
the resistor is the maximum resistance while the fully on FET represents the lowest resistance.

what do you mean by a cross coupled compactor?
 

Dr_Mohammad

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the hysteresis is a voltage-band defined in op-amp comparators which determines the output level based on the non-inverting input. if you won't to use hysteresis, the output will go to chattering and will be unstable. because the input is always under changes and noises.
 

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