Selecting the correct oscillator/multivibrator circuit

Discussion in 'Digital Circuit Design' started by Ilya Gulko, Aug 3, 2016.

  1. Ilya Gulko

    Thread Starter New Member

    Jul 13, 2016
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    Hi everyone,

    I am not experienced with electronics, but my project requires to purchase/build a device that:
    1. Will convert a DC signal of few volts to AC signal of few volts.
    2. Will have a frequency in the range 50kHz - 170kHz (variable frequency preferred).
    3. Will generate a clean and stable square or sine wave of the specified frequency.
    4. Is compact and lightweight.

    The closest devices I found were oscillator circuits and multivibrators, but there are many types and many ways to build them into a circuit. Could anyone recommend a device and circuit that will best satisfy the above requirements?

    Thank you so much!
     
  2. ian field

    Distinguished Member

    Oct 27, 2012
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    There were various TTL VCO chips, but I'm not sure how many are still available, 74LS629 might be one of them. There's almost certainly CMOS types available.

    Probably the simplest you can cobble together is the basic 2 transistor astable. Just gang the 2 base resistors to the wiper of a pot across the supply rails and you can vary the frequency - its a basic VCO, but the input range isn't rail to rail. If you take it too low the oscillator will stop.

    If you need more than logic level output voltage - buffer the output with an open collector buffer and put a casc-ode style common base on it.
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
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  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    The simplest square-wave generator, ~30kHz-200kHz :-
    SquareGen.JPG
    Operates from a 3-15V DC supply (not shown).
    A clean, stable sine-wave of that frequency range is much trickier to generate.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    What distortion can you tolerate on the sinewave?
     
    thumb2 likes this.
  6. AlbertHall

    Well-Known Member

    Jun 4, 2014
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  7. hp1729

    Well-Known Member

    Nov 23, 2015
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    Buy one. Do you have a budget it has to fit in?
     
  8. Ilya Gulko

    Thread Starter New Member

    Jul 13, 2016
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    Anything within reason. I'd rather it cost $20 at most.
     
  9. hp1729

    Well-Known Member

    Nov 23, 2015
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    Here's a start then, XR2206. carried by Jameco Electronics and others.. Price about $8.00, Jameco used to have a kit about in your price range.
     
  10. AlbertHall

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    Jun 4, 2014
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    See post #6
     
  11. hp1729

    Well-Known Member

    Nov 23, 2015
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    Ah, yes. You beat me to it. Jameco kit with the XR2206 is about $28.00. "JE2206, p/n 20685". State side distributor.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    There used to be the ICL8038 and the "improved" MAX038, sadly both discontinued.

    There maybe NOS vendors (expensive) or they occasionally turn up in discarded waveform generators - as does the XR2206.

    The 4046 CMOS PLL also contains a VCO.
     
  13. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Also see post #6, £2 to £3 (UK) from ebay, kit or assembled
     
  14. ian field

    Distinguished Member

    Oct 27, 2012
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    One of them claims to be offering a DDS 8038.

    Nonetheless - DDS is another option that I don't recall having seen yet.
     
  15. AlbertHall

    Well-Known Member

    Jun 4, 2014
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  16. hp1729

    Well-Known Member

    Nov 23, 2015
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    I guess it is a small thing these days but the original poster is in Ohio.
     
  17. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    What is this for?
    What does the output signal drive?
    What is the available power source (volts, amps)?
    Is this a school project? If so, which school?

    ak
     
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