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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: incredible comparator behaviour
Date: Wed, 08 Jan 2003 22:54:16 GMT
NNTP-Posting-Date: Wed, 08 Jan 2003 17:54:16 EST
> Good Morning,
> I try use a MAX942 comparator. this is a dual fast comparator with internal
> Normally a simple to use device.
> 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.
> I need to rise the threshold at 3V to avoid the pulse at the output.
> (the scope used to see the signals is 500MHz bandwidth)
> (power supply is 5V, threshold perfectly stable)
> (I tried several chips)
> Can anyone help me on this incredible behaviour?
> Thank you very much.
Your description of the problem is not entirely clear to me, so please
try again to describe what is happening to someone who has no idea.
In the mean time, how close is the supply bypass capacitor to the
power pins of the chip?
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