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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Is anybody using NE521 comparators?
Date: Thu, 26 Sep 2024 01:17:14 +1000
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On 25/09/2024 11:16 pm, Jean-Pierre Coulon wrote:
> If the difference between both inputs is not a least 50 mV the output 
> remain at about 1.5 or 2V instead of beeing close to V+ or ground. What 
> am I doing wrong?

Getting it to oscillate faster than your oscilloscope can follow?

The NE521 is quite fast - it can get up to 55MHz - and it's not 
difficult to make it self-oscillate if the voltage difference between 
the input isn't high enough to swamp capacitative feed-through or ground 
loops.

I've had to crawl through circuits which were in production when a batch 
of faster comparators - not NE521 parts - showed up a marginal layout. 
And tightening up the layout didn't always keep on working.

-- 
Bill Sloman, Sydney