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
Date: Thu, 9 Jan 2003 17:00:50 +0100
Organization: Wanadoo, l'internet avec France Telecom
NNTP-Posting-Date: 9 Jan 2003 16:00:21 GMT
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
First, thank you for interest.
I must add precisions:
I use a self routed PCB (double side FR4) with a ground plane on the
All traces are on the top-side.
the comparator VCC is bypassed with a ceramic 100nF capacitor.
reference voltage is tuned with a 10k trimmer and filtered with a 100nF
the signal is high-pass filtered with a 100nF - 100R cell.
All of those components are distant of < 1cm.
If the device is oscillating, it is not visible, since the output is stable
without pulse on the input.
(I must agree the impedence of both inputs are not the same but can this
explain the entire thing?)
"Martin" a écrit dans le message news:
> Good Morning,
> I try use a MAX942 comparator. this is a dual fast comparator with
> 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
> 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.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup