Monday 29 August 2016

operational amplifier - Is there a name for this kind of comparator?


I have two analog signals, and I need to generate digital signal (to use as an interrupt for an MCU) when the voltages differ more than a certain amount. It's going to be some sort of comparator arrangement, but does this have a name? Window comparators are in the right kind of area, but aren't differential.



Answer





does this have a name?



Yes, it is a window comparator even though you think it isn't. Regular window comparators have one "variable" input but there's nothing wrong with the "fixed" input being variable too. Consider this "regular" circuit: -


enter image description here


If the middle of the three resistors were, in fact, two resistors in series (with the new input feeding the centre-point) then you get a window (magnitude) comparator. Depending on precisely how you want this to work you can make the two outer resistors into a current source and a current sink and you could even use something like a TL431 across the full width of the middle resistor to define precise thresholds above and below the new reference input.


It's still a window comparator.


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