experience with LM 380N
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Posts: 46,084
Hello,
I have a network of 12V intercom systems which use the LM380N
chip. I was wanting to use the stamp to convert the signal to
digital and send it over fiber and then convert it back to copper.
However, I have no experience with the LM380N and no little about
audio and impedance matching. Does anyone have any experience with
this or could point me in the right direction?
Thanks,
Heath
I have a network of 12V intercom systems which use the LM380N
chip. I was wanting to use the stamp to convert the signal to
digital and send it over fiber and then convert it back to copper.
However, I have no experience with the LM380N and no little about
audio and impedance matching. Does anyone have any experience with
this or could point me in the right direction?
Thanks,
Heath
Comments
Someone here may be able to help you. Sorry, not me. You might also
post the question to
http://groups.yahoo.com/group/Electronics_101
if you haven't already done so.
Good Luck,
Frank
--- In basicstamps@yahoogroups.com, heathlovell@y... wrote:
> Hello,
> I have a network of 12V intercom systems which use the LM380N
> chip. I was wanting to use the stamp to convert the signal to
> digital and send it over fiber and then convert it back to copper.
> However, I have no experience with the LM380N and no little about
> audio and impedance matching. Does anyone have any experience with
> this or could point me in the right direction?
> Thanks,
> Heath
much about impedance matching to the chip. Just drive it with a level equal
to that from the microphone circuit and you should have no problems. Couple
to the chip input with a capacitor (10-100 uF)and you should have not
problem. Another use for the Lm380 is as a tracking voltage divider. If
you connect the Lm380 to 12 vdc, the output will float at 6 volts. This is
useful for running op amps from a single supply as this can generate the
reference for the + input.
jim
http://www.geocities.com/jimforkin2003/
Original Message
From: franksmith512 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ljI0mz8cQADVU5cVbDEpOR2iUvUMSaPcyTvMDqs2jQl5hQq5Ijfsb2FmN7dKNJefgYUqxoiFf4i3S8xUc4m5]franksmith512@y...[/url
Sent: Monday, February 23, 2004 8:57 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: experience with LM 380N
Hey Heath,
Someone here may be able to help you. Sorry, not me. You might also
post the question to
http://groups.yahoo.com/group/Electronics_101
if you haven't already done so.
Good Luck,
Frank
--- In basicstamps@yahoogroups.com, heathlovell@y... wrote:
> Hello,
> I have a network of 12V intercom systems which use the LM380N
> chip. I was wanting to use the stamp to convert the signal to
> digital and send it over fiber and then convert it back to copper.
> However, I have no experience with the LM380N and no little about
> audio and impedance matching. Does anyone have any experience with
> this or could point me in the right direction?
> Thanks,
> Heath
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stamp emails.
This one about impedance matching with audio amps caught my attention, since
it's a subject I actually know something about.
The idea a impedance matching an audio circuit is largely overemphasized
nowadays. Back in the early days of Ma Bell and the phone system, amplifiers
were very expensive, so transferring and conserving power was important.
Consequently, a lot of transformers were used to step-up, step-down, and
balance voltages. But with the advent of really cheap amplifiers (pennies,
if that) we don't need to impedance match most audio circuits, even when
interfacing to a digital circuit. Most Op Amps and such are run in bridging
mode, where the output impedance of one stage (a few hundred ohms or less)
drives a relatively high input impedance of the next stage (10,000 ohms or
more). So we're not actually transferring power, only sending a reference
voltage. That means you can use a stamp to drive the input of any audio op
amp without a true impedance match, but you WILL need the proper pull-up or
pull-down resistor to make the stamp output stage happy itself. Going the
other way, any Op Amp will be fine driving the input of a stamp, and you
only have to worry about the voltage level not exceeding TTL limitations.
That's why a clamping diode and series limiting resistor are good ideas.
Of course, if you DO USE any sort of transformer in the circuit, it needs to
be properly terminated (impedance matched) or really bad ringing will be the
result. And very long transmission lines (thousands of feet) store enough
energy at audio frequencies that end termination may be required to keep the
whole thing from bouncing around. This is due to the series inductance and
parallel capacitance of long wire runs with insulation separating the leads.
Also, for RF (Radio Frequencies) proper termination is a must have. Remember
that microprocessors essentially run at RF rates, so terminating everything
properly when going in and out of the box could make the difference between
success and failure.
Mike Sokol
mike@f...
www.fitsandstarts.com
" One should not increase, beyond what is necessary,
the number of entities required to explain anything"...
-William of Occam-
Original Message
From: <heathlovell@y...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, February 23, 2004 8:47 PM
Subject: [noparse][[/noparse]basicstamps] experience with LM 380N
> Hello,
> I have a network of 12V intercom systems which use the LM380N
> chip. I was wanting to use the stamp to convert the signal to
> digital and send it over fiber and then convert it back to copper.
> However, I have no experience with the LM380N and no little about
> audio and impedance matching. Does anyone have any experience with
> this or could point me in the right direction?
> Thanks,
> Heath
>
>
>
> To UNSUBSCRIBE, just send mail to:
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> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
> Yahoo! Groups Links
>
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