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OP AMP voltage multiplier

Discussion in 'Electronic Basics' started by Ahmed Samir, Jul 3, 2003.

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  1. Ahmed Samir

    Ahmed Samir Guest

    Hi there

    is it possible to realize a four quadrant voltage multiplier-for audio
    signals- using an op amp or two?if so how and if it's not possible what's
    the easist way to do it??

    thanks very much
    ahmed samir
  2. AD633JN from Analog Devices. For best thd, use the
    Y-inputs for the audio, and keep the ac input signal
    below about 5Vrms.
  3. Bill Sloman

    Bill Sloman Guest

    The AD633 is clearly what the OP needs, but it isn't the op amp that
    he is asking for, and it is probably worth mentioning that a
    four-quadrant multipler is a non-linear device, and op amps - as such
    - aren't designed for non-linear applications. After all, this is
    cross-posted to sci.electronics.basics where you can't assume any
    background knowledge of electronics.
  4. OpAmps cannot do this, have a look at the multiplying DACs.

  5. Bob Masta

    Bob Masta Guest

    Not possible with an ordinary linear op-amp. The usual
    approach uses an array of matched transistors (plus a
    couple of op-amps). Try a Web search for 'Gilbert Multiplier'.

    There are also Operational Transconductance Amplifiers
    (OTAs) like the CA3080 and LM13600 that are often used
    to create multipliers, but usually just 2-quadrant..

    Depending on exactly what you are shooting for, there are
    a number of tricky approaches, including diode ring (bridge)
    multipliers, FETs as voltage controlled resistors, pulse width
    modulation, log-antilog, etc. Tell us more about your application and
    maybe we can pick out the simplest/best approach.

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Shareware from Interstellar Research
  6. Everything is possible, but probably not worth to.
    The accuracy and the distortion are going to be about 1% best to best.
    I would advise to use DSP instead of messing with analog.

    Vladimir Vassilevsky, Ph.D.

    DSP and Mixed Signal Design Consultant
  7. I reason your opinion is a obviously a bit biased here. I would guess
    that the poster wants a *simple* solution. i.e. one without spending 6
    months with development systems.

    To the poster. Analog Devices SSM audio VCA parts are pretty good. They
    used to be PMI ones, which used to be...

    Kevin Aylward
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
  8. Precious Pup

    Precious Pup Guest

    And it is probably worth mentioning too that BS has never taken a Signals and Systems course, along with never
    taking ECON101.

    Show the following system to be either linear or non-linear:

    The System
    | |
    in | /¯¯¯\ | out
    x(t) O--------( X )---------O y(t)
    | \___/ |
    | | |
    | | |
    | O |
    | cos(w_c·t) |

    Included and inside the system is a "4-Quad" multiplier.
    Bonus points: Show the system to be either time-invariant or not.
  9. Ben Bradley

    Ben Bradley Guest

    With a diode 'ring modulator', maybe...

    You're just trying to drum up DSP business, aren't you? ;)
    MC1496 from, cheap, usable, still available in DIP (!),
    less distortion than a diode ring modulator, and the company only used
    to be one other company...
  10. Jim Thompson

    Jim Thompson Guest


    How appropriate, "BS" ;-)

    But "BS" has taken all the Commie and Socialism courses ;-)

    ...Jim Thompson
  11. Bill Sloman

    Bill Sloman Guest

    Ah. More jokes from primary school. Concentrate on electronics, Jim -
    you are pretty good at that.

    Oddly enough, I've not taken any Commie or Socialism courses either -
    as with electronics, if there has been something I need to know I go
    off to the library and read about it.

    I used to be embarassed about my lack of formal qualifications, but
    after you have supervised a few new graduates you get some idea of how
    little of their coursework actually sticks, and I stopped worrying. It
    never worried the IEEE at all.

    I wonder if Peurile Pup has ever published anything in a refereed
    journal - let alone had it cited.
  12. Ben Bradley

    Ben Bradley Guest

    Oh, you want to make a "Voice Scrambler." This crude ASCII block
    diagram should demonstrate it:

    IN --->[300Hz-3kHz bandpass filter]--->[4-quadrant multiplier]--->out
    3.3kHz sine wave

    For the bandpass filter, cascade a simple R-C 300 Hz high-pass with
    a two-pole or three-pole low-pass filter from Lancaster's "Active
    Filter Cookbook."
    This circuit will work for both encoding and decoding.
  13. Precious Pup

    Precious Pup Guest

    Now that's an accomplishment. You can get deluded just fine without bothering with school.
    It isn't your formal qualifications you should be embarrassed about. You should simply be embarrassed about
    being a persistant dumbass.
    Retard, I don't claim to be original, creative, smart, clever, and whatever else you fantasize yourself to
    be. I don't really care. I try to get folks to give me money in exchange for effort/labor -- that's about

    Let me publish more right here for you:

    Compare and contrast the two systems.

    The System
    | |
    in | /¯¯¯\ | out
    x(t) O--------( X )---------O y(t)
    | \___/ |
    | | |
    | | |
    | O |
    | DC=2 |

    The System
    | |
    in | |\ | out
    x(t) O--------| >-------------O y(t)
    | |/ |
    | Op-amp set to |
    | a gain of two |

    Are these systems linear?
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