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single ended signal to differential signal?

Discussion in 'Electronic Repair' started by Rüdiger Leibrandt, Apr 18, 2007.

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  1. 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.
     
  2. Unbalanced to balanced? What is the signal? And just how far are you
    sending it using which cable?
     
  3. 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.
     
  4. Eeyore

    Eeyore Guest

    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
     
  5. Eeyore

    Eeyore Guest

    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
     
  6. 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.
     
  7. Eeyore

    Eeyore Guest

    I understand.

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

    Graham
     
  8. 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
     
  9. 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!
     
  10. GregS

    GregS Guest

    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
     
  11. Eeyore

    Eeyore Guest

    This is not ideally suited to this task.

    Graham
     
  12. Sofie

    Sofie Guest

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

    DaveM Guest


    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.
     
  15. Guest

    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
     
  16. 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.
     
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