oscilator to DC circuit help!!!

Discussion in 'General Electronics Chat' started by jericko, Apr 23, 2008.

  1. jericko

    Thread Starter Member

    Apr 21, 2008
    16
    0
    ok, here's what this is, its a colpits oscilator at about 3k actually its 2.777khz if memory serves me right, anyway the second stage is a buffer with a filter coupler between the oscillator and buffer then the last stage is a amp to "buff" the oscillations. anyway im having trouble with converting it to a stable dc voltage at any given load. i use multi sim student edition, dont know the version but it will only let me add so many parts. so i cant test it on anything virtually that is. and dont realy have the components to do it myself, broke spent the last of my money for supplies needed for bootcamp. anyway any idea's on how to make it more stable at any given load, well anywhere between 1 Ohm and 1M Ohm.

    [​IMG]

    if its hard for you to see here's the link

    http://img.photobucket.com/albums/v104/jerickoshu/colpits2.jpg
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, you have the rectifier portion connected wrong.

    D1 has the cathode connected to ground - basically, you need to switch places with the 47uF cap and D1 - but you also need a resistor to ground to act as a load.

    With just the Colpitts oscillator section modeled, LTSpice's FFT indicates a frequency of 2,888.9 Hz.
     
  3. jericko

    Thread Starter Member

    Apr 21, 2008
    16
    0
    that somewhat fixes my problem except now my output is positive, i want a negative voltage out of it. i think i forgot to mention that sorry.
     
  4. jericko

    Thread Starter Member

    Apr 21, 2008
    16
    0
    is it even possiable to use a colpits oscilator as a reliable neg. dc output?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    What are you really trying to do, make a negative supply from a positive voltage? How much current and what voltage?
    You'll either have to use switching capacitors or inductors to do that.
    There are ICs available that all you have to do is hook up a few external components, and you're done.

    Are you building this from discrete components for a learning exercise?

    Which bootcamp? When I went, all I took with me was the clothes on my back and $20 in cash for a 2,300 mile trip!
     
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