Paul Ciszek
Guest
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 Posted:
Mon Oct 10, 2005 11:46 pm Post subject:
Questions about Differential Line Receivers |
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I have a detector with pairs of output lines: Q and Q NOT.
I am told that I need to look for a 5V difference between Q and Q NOT
in order to record an event; just watching for Q going high is not
good enough, Q NOT has to go low at the same time. This is in order
to separate signal from noise. These pulses should last for 2us give
or take a us.
I am told that a Differential Line Receiver should be able to do
this; however, the data sheet for one such:
http://focus.ti.com/lit/ds/symlink/sn75115.pdf
....leads me to believe that the output goes high whenever A goes
higher than B, not when A is some threshold higher than B. Can
one of these be jiggered to use a fixed voltage threshold, i.e.,
the output goes high only when A is 4 volts higher than B?
The other approach would involve op-amps used as a differential
amplifier and a schmidt trigger. Can anyone recommend an op
amp that would respond quickly enough? Single supply would be
nice, though not absolutely necessary.
--
Please reply to: | "Mundus Vult Decipi"
pciszek at panix dot com | ("The world wants to be deceived")
Autoreply has been disabled | --James Branch Cabell
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Watson A.Name - \"Watt Su
Guest
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| Posted:
Mon Oct 24, 2005 8:35 am Post subject:
Re: Questions about Differential Line Receivers |
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"Paul Ciszek" <nospam@nospam.com> wrote in message
news:dieug6$pdk$1@reader1.panix.com...
| Quote: | I have a detector with pairs of output lines: Q and Q NOT.
I am told that I need to look for a 5V difference between Q and Q NOT
in order to record an event; just watching for Q going high is not
good enough, Q NOT has to go low at the same time. This is in order
to separate signal from noise. These pulses should last for 2us give
or take a us.
I am told that a Differential Line Receiver should be able to do
this; however, the data sheet for one such:
http://focus.ti.com/lit/ds/symlink/sn75115.pdf
...leads me to believe that the output goes high whenever A goes
higher than B, not when A is some threshold higher than B. Can
one of these be jiggered to use a fixed voltage threshold, i.e.,
the output goes high only when A is 4 volts higher than B?
The other approach would involve op-amps used as a differential
amplifier and a schmidt trigger. Can anyone recommend an op
amp that would respond quickly enough? Single supply would be
nice, though not absolutely necessary.
|
The line receivers used in the boxes we used long ago at work were LM710
and Signetics NE529. They may be hard to come by today, so a more
recent substitute is probably better.
| Quote: | --
Please reply to: | "Mundus Vult Decipi"
pciszek at panix dot com | ("The world wants to be deceived")
Autoreply has been disabled | --James Branch Cabell |
|
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