VCO question

Discussion in 'General Electronics Chat' started by Tiger, Sep 24, 2004.

  1. Tiger

    Thread Starter New Member

    Sep 24, 2004
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    0
    :D Hello everyone, first time here...

    I am looking for a Voltage Controled Oscillator with sinusoid output, all the VCOs I could find from Digikey provide only square wave output. Does anyone know where I can get such VCO chips? Or I'll have to build some circuit myself to convert the square wave to sine wave? My frequency range is a few tens of Khz. Thanks a lot~
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Get a ICL8038CCPD from Mouser. It's a function generator, with sine, triangle and square outputs in quadrature. Intersil made it, so you might get a data sheet from them (they've been eaten up, so I hope you can still find a link to them).

    The output is weenie for load, but there are adjustments for symmetry and duty cycle. Just buffer the output with an op amp.
     
  3. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi,

    i would also recommend XR2206 in case you would have a problem with the 8038. it is also a function gen. they also have this 8038. :)

    Function Generator

    :D
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    The salient difference between the XR2206 and the 8038 is frequency. Maybe I'm misremembering, but I think the 2206 is a high frequency device, and won't run under several tens of kilohertz.

    Sine output VCO's are getting hard to find.
     
  5. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi

    the 8038 is qualified as a precision waveform generator and can go as low as 0.001Hz and can go as high as 200Khz thru external means as claimed but i have never tried going that low to check whether its true. likewise the 8038 can be tap simultaneously for its sine, sq. and triangle output.


    the 2206 is not qualified as a precision waveform gen. but simply as a waveform gen. and its output is from 0.01Hz to as high as 1Mhz thru external means. output can be utilized on a one by one function only.

    between the two units, they have their own strenght and weakenesses. the 2206 has an FSK function but the 8038 does not. the 8038 has better supply stability than the 2206 but the difference is negligible. :)
     
  6. Tiger

    Thread Starter New Member

    Sep 24, 2004
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    0
    :) beenthere and mozikluv, thank you guys so much!! I've looked through the datasheet for both 8038 and 2206, since I don't require large frequency scan range (I only need +/-5kHz around 75kHz), both should work fine for me. The 2206 is much cheaper though so I've ordered a few and gonna try it out as soon as I receive them.

    :unsure: One drawback (for me at lease) of these chips is that both of them require >=10V supply. I was going to make my whole circuit as one board supplied with single 5V, it's not critical but just feel nicer. I'm thinking about make some squre-to-sine wave converter but could find very few examples online. Do you know about such kind of circuit that would work for my frequency range? Thanks again!
     
  7. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi tiger,

    just holler if you need help in the circuit design of the 2206. just curious, why do you still need the square to sine converter? :)
     
  8. evilxyzzy

    New Member

    Dec 15, 2004
    1
    0
    This is my first post here. I saw this topic and had to reply because its something near and dear to me...

    The 8038 runs warm. Very warm. However a guy by the name of Thomas Henry came up with a nifty workaround for the 8038 that gives wide linear responce *and* runs the chip very cool.

    http://www.midwest-analog.com/diylvco.html for a schematic.

    Worth a look. There is a chance that the XR2206 can be treated in the same manner. Rumor has it that he'll be releasing a book specifically on torturing 8038's and 2206's for use as stable linear VCOs ( and expo VCOs if you add an expo converter ). He already has a book for tormenting 566's but they are getting to be a rare beastie these days.
     
  9. phillyfatass

    New Member

    May 5, 2005
    1
    0
    I am designing an AC power supply to produce a sine wave at 50-400Hz. Is there anything more modern than the 8038 or 2206? As it is a new design I am caoncerned it may become obselete like the Intercil ICL8038 did.

    Also, any ideas on how to control the output amplitude with a DC voltage?

    If anyone of you clever people can help I would be truly grateful.
    Many thanks.
     
  10. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    The 8038 is still widely available as far as I know, but I found the 2206 easier to use. Although it wouldn't be a concern for your requirement, it is impossible to get a 1000:1 frequency sweep with the 8038 without sacrificing sine purity at the low frequency end. I washed my hands of it.

    You might find something of interest in the unit I put together
    here.
     
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