The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
Subject: Re: incredible comparator behaviour
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Thu, 09 Jan 2003 14:07:09 GMT
NNTP-Posting-Date: Thu, 09 Jan 2003 15:07:09 MET
Paul Burke wrote:
> Martin wrote:
>> I try use a MAX942 comparator. this is a dual fast comparator with
>> internal hysterisis.
>> 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 internal hysteresis.
>> 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.
This sounds very much like gnd-bounce or oscillations to me. The supplies
have to be filtered by some nice ferrite beads (in V+ and Vcc to 5V), the
bypass capacitor must be a very small(0.1u/0603size) ceramic, directly on
the Vcc and gnd pins. Analog gnd plane with bypass cap between +V and -V. In
a breadboard these parts won't work.
electronic hardware designer
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup