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Sine wave generator

Discussion in 'Electronic Design' started by [email protected], Aug 15, 2006.

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  1. Guest

    Hi,

    I need to design a simple variabel sine wave generator up 100kHz. Does
    anyone know of single chip solution? If nt any ideas how to design one
    with minimal chip count?

    Thanks a lot

    Joseph Zammit
    Malta
     
  2. You can do it with one op-amp that has a gain well over 3 at 100 kHz.
    Google for 'Wien Bridge'. The problem is not getting it to oscillate but
    controlling the amplitude so you don't get a clipped sine wave. There
    are many ways of doing it; the best, but costly, is a vacuum thermistor
    bead. You can use a FET as a voltage-controlled resistor.

    It won't do 0 to 100 kHz in one range, though. If you want that (I can't
    think why), Google for 'Exar function generator'. but it's not as much
    fun as the Wien bridge solution.
     
  3. Luhan

    Luhan Guest


    http://www.intersil.com/data/FN/FN2864.pdf

    Luhan
     
  4. You don't learn anything much from using one of them. And it costs far
    more than an op-amp, probably as much as a bead thermistor.
     
  5. Joel Kolstad

    Joel Kolstad Guest

    If you want an "almost all digital" solution, Analog Devices has
    microcontrollers with built-in DDS generators that will easily meet your
    specifications. (See:
    http://www.analog.com/en/press/0,2890,3%5F%5F96529,00.html) This is
    probably serious overkill, however, and certainly not the cheapest solution
    and nowhere close to the lowest power. The main benefit over, e.g., a wien
    bridge is that you simply program the output frequency with a digital word,
    and the result is as accurate as your (e.g., crystal) clock source (if
    accuracy was unspecified, a crystal is generally considered "far more than
    accurate enough, with no calibration or drift to worry about...").
     
  6. Leon

    Leon Guest

    A software DDS running on a suitable MCU and DAC should be suitable. An
    AT90S2313 clocked at 10 MHz should be able to manage 100 kHz.

    Leon
     
  7. Phil Allison

    Phil Allison Guest

    ** Groper alert !!


    ** Variable by what means ?

    A knob?

    A control voltage.

    A light beam ?

    ESP ???



    ** Tell us what is the actual problem first.

    Or be condemned to hell for eternity as another TROLL.>





    ........ Phil
     
  8. Tim Wescott

    Tim Wescott Guest

    Search around for the tiniest incandescent lamp you can find -- if you
    can find a 6V grain-of-wheat bulb you can use that for the resistive
    element. I suspect a small thermistor stuck in foam would work almost
    as well as the vacuum thermistor, and possibly better than the lamp.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  9. BobG

    BobG Guest

    I need to design a simple variabel sine wave generator up 100kHz.
    =====================================
    I recall Mr Hewlitt and Mr Packard made a Very Able sine wave
    oscillator back in the day... in Palo Alto as I recall....
     
  10. Yes, the 8038

    Rene
     
  11. need a bit more info:

    variable over what frequency range? Continuously variable? By ranges?
    Down to 0.001 Hz?

    How stable in amplitude and frequency? How good a sine wave? What
    percent distortion? What output voltage? What kind of load?
     
  12. Yes, but amplitude control by incandescent lamp is possible with
    valves/tubes, but not with normal op-amps.
     
  13. Ken Smith

    Ken Smith Guest

    Wien bridges aren't super easy to control the frequency on. A quad
    op-amp version of the 3 opamp "state variable" oscillator may be a better
    option for the OP.

    I will even try to ASCII art draw it

    R1 /+!---GND
    ---/\/\--+---< !
    ! ! \-!--
    ! ! R3 !
    ! ---/\/\--+
    ! R2 !
    +--/\/\--+---/\/\/--
    ! ! R4
    +---!!---+
    ! C1A ! C1B
    R5A ! ! ---!!---
    --/\/\-+-!-\ ! R5B ! !
    ! ! >---+----/\/\----+-!-\ !
    ! GND--!+/ ! >---+
    ! GND-!+/ !
    ! ---/\/\---+----/\/\----------------
    ! ! R6 ! R7
    ! ! /-!----
    --+-< !
    \+!---GND


    Normally:

    R6 = R7

    R1 > 5*R5

    R2 = 0.8 * R1

    R3 = 1.3 * R4

    R5A and R5B can include a POT like this:


    ----
    !
    \
    / <---/\/\---
    \
    !
    GND
     
  14. Indeed, it's better but not 'simpel', which was the spec.
     
  15. Fred Bartoli

    Fred Bartoli Guest

    Never seen an opamp Wien bridge controled by incandescent silicon?
     
  16. In message <44e2d4ff$0$22822$>, dated Wed, 16 Aug
    2006, Fred Bartoli
    No, I use a current-limited power supply. For incandescent silicon, you
    need 1 kW audio amplifiers, or 5 kW lamp dimmers.
     
  17. Jim Thompson

    Jim Thompson Guest

    For oscillators my gyrator BP works best... behaves just like a real
    tank.

    ...Jim Thompson
     
  18. Rich Grise

    Rich Grise Guest

    Sherman, or Panzer? ;-)

    Thanks,
    Rich
     
  19. Nico Coesel

    Nico Coesel Guest

    A microcontroller with an 8 bit (R2R) DAC.
     
  20. Ken Smith

    Ken Smith Guest

    I work with someone who invented the "light emittng PROM". Way back when
    EPROMs had a window so you could erase them with UV.
     
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