single ended signal to differential signal?

I posted this a bit earlier in sci.electronics.design, but this list seems
to be more alive at this time of the day:
I need to convert a single ended signal to a differential one. Theres is
plenty of documentation on the other way ( differential to single ended )
but I am lost regardign info on my problem. Anyone has some info or links
to this topic? I need to both amplify the signal and boost it over the
line.

Any help or suggestion appreciated.

 

Unbalanced to balanced? What is the signal? And just how far are you
sending it using which cable?

 

Okay: the signal is a few millivolts around 2V, but it can go up to full 5
Volts in the extreme case. The cable used is a category 5 cable, about, I
think, 8 meters in length. I'm just the poor guy having to solder it all
together, so I can at this time not make much from the terms balanced or
unbalanced. With an average of 2V the signal has a definetive offset, and
it needs being DC coupled into the TL072 acting as line driver for the
differential line. I find no infos on the net for that kind of setup, and
it wonders me, for there are tons of scenarios where the reverse is being
done.

 

Single ended

Differential (audio terminology)

Is it an AC signal riding on a DC level ?

What kind of signal are you dealing with here ?

Graham

 

One simple answer is to have another 1/2 TL072 wired as a unity gain inverter
driven from the original output, driving the other input of the differential
amp. Note the 6dB extra gain you get this way.

I'm not entirely clear why this is necessary over only 8 metres of cable run
though. Are there interfering signals ?

Graham

 

There is the basic concept:
http://www.aries.homeftp.net/publish/Electronics/concept.jpg
The opamp on the right side is just to symbolize the input of the PC-card
where the sampling takes place. It's software can control the impedance and
other aspects of the cards inputs.

The signal is from a K-Band Transceiver, a small radar. And the noise I get
on the lines that run through a room filled with servers is enough to add
so much ambient noise that single opamp "boosted signals" contain too much
noise than to make use of the values received, for then stronger signals
would produce clipping.

 

I understand.

What is the bandwidth of the signal ? Is it purely an AC signal or do you *need*
DC coupling ?

Graham

 

Then you ask where it belongs, in sci.electronics.basics

THis isn't about basics, this isn't about design, this newsgroup is
about the repair of electronic equipment.

Read Mark Zenier's guide to the hierarchy before you mispost again:
ftp://ftp.eskimo.com/u/m/mzenier/seguide9706.txt

MIchael

 

Okay - the last word after a lot of datasheet reading is now a MAX435 - it's
a wideband Transconductance Amplifier.
I just need to find out how to give it a variable gain without ruining the
impedance of it's output, and then I am fine.

Thank you all very much for the help you provided to me!

 

There would be many chips you could use. You can even use a TLO72,
but usually one with a more heafy output drive is used.
What is the terminating Z ? What is the response needed?

greg

 

This is not ideally suited to this task.

Graham

 

Michael....
Not so fast here ! .... let us not get so specialized and so quickly send
people off to other newsgroups.
There are plenty of folks on this "repair" newsgroup that are not only
qualified to answer these types of "design" questions but also are very
happy to contribute.
Most repair techs have always had some design and installation experience
and can many times propose a simple, practical and workable solution that
some design people sometimes ignore in favor of a more complicated,
engineering eloquent and troublesome solution.
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - -



snipped:
you ask where it belongs, in sci.electronics.basics

 

You still haven't said what the signal is. Audio? Video? SHF? ;-)

 

Take a look at the Analog Devices SSM2142 Balanced Line Driver
(http://www.analog.com/en/prod/0,,765_1075_SSM2142,00.html) for the single-ended
to balanced line (differential) function. AD also has a mating differential
line receiver, the SSM2141 High Common-Mode Rejection Differential Line Receiver
at (http://www.analog.com/en/prod/0,2877,SSM2141,00.html). These units are
quite good at handling high common-mode signals (induced noise).

Since you haven't mentioned the exact nature of your signal, such as frequency
range, required gain and gain accuracy, etc, I'm assuming that it's in the audio
range, and gain accuracy is a secondary consideration. These two units are
designed specifically for professional quality audio equipment, and will easily
fit that requirement.
If your signal requirements are different, such as video, digital, etc, then you
need to come back to us for a more meaningful answer. We can't give precise
answers to ambiguous questions.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.

 

I dont think youre giving the required information, its all very
unclear, both here and in your follow up.

So I'll just mention a general principle: interference can be more or
less wiped out by reducing line driver impedance. With low impedance
drive, runs far longer than 8m are possible with single ended signals.

Opamps do not give as low z output as would be ideal. If your signal
is in the af band, an audio amplifier may be a simple low cost way to
get R_out in the region of an ohm or less.


NT

 

It's a radar - The frequency varies with the speed of items approaching or
moving away, the distance they are away, and such stuff - its a tiny
doppler-radar. I have - honestly no clue, for there is no information upon
the maximum frequency-shift in this manual, nor does my boss know what
things he actually wants to focus on.

It is a InnoSent IVS24-2-4-2-162 K-Band VCO Trasceiver

The MAX will do it's job pretty well - DC coupled and capable to transmit up
to 200MHz - more our digitizer-card cannot handle anyway.