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From: Paul Burke
Subject: Re: incredible comparator behaviour
Date: Thu, 09 Jan 2003 08:51:28 +0000
Organization: Scazon Systems
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> I try use a MAX942 comparator. this is a dual fast comparator with internal
> Normally a simple to use device.
They are VERY fast and incredibly sensitive to parasitic feedback. It's
easier to make them oscillate than to operate properly, despite the
> But I encounter strange problems.
> I want to detect (at IN- pin) pulses of 1.2V High and about 100ns wide (rise
> time about 15-20ns).
> But when I fix a threshold of 1.4V at IN+, the device is switching and I
> have a pulse at the output.
> The height of the pulse is decreasing when I rise the threshold.
You have noise somewhere- either power rails, reference or signal. It
could also be feeding through from the other comparator in the package.
What is the impedance of the signal lines? I have found this needs to be
very low, or the line picks up wisps of RF and the output yammers away.
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