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Square wave oscillator help please.

Discussion in 'Electronic Basics' started by John Popelish, Jul 25, 2004.

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  1. Sorry, I cant find any reference to a square wave oscillator on this
    page.
     
  2. If you download the datasheet in PDF form, then it's in the bottom right corner
    on page 5 of the amplifier datasheet.

    Jon
     
  3. Thank you. Adjust the size of the capacitors by 1/40.
     
  4. It's on the datasheet (page 5) http://www.national.com/ds/LM/LM386.pdf

    Best regards,
    AM
     
  5. You are probably looking for this, time period of square waves is

    T=2*RC*In((2R1 + R2)/R2)

    Where in the original schematic
    R=30k, C=.1u, R1=1k and R2=10k

    Adjust these values which suit you the best.

    Best regards,
    AM
     
  6. Rubicon

    Rubicon Guest

    Hello,

    Can anyone help me change this LM386 1kHz square wave oscillator to
    40kHz? Formulas or a walk through?
    PDF Page 5 http://www.national.com/pf/LM/LM386.html

    There's nothing that I can find in the PDF to help me and searching
    has found mainly square wave or amplifier kitsets.

    Regards,

    Andrew.
     
  7. Rubicon

    Rubicon Guest

    Thankyou for the help.

    I apologise for not being specific enough, it's something I must
    attend to.

    Regards,

    Andrew.
     
  8. Rubicon

    Rubicon Guest

    So:

    0.1uf / 40 = 0.0025uF
    50uF / 40 = 1.25uF

    Both non standard values in my catalogues. Time to work out parallel
    caps?

    0.0015uF + 0.001uF = 0.0025uF
    1uF + 0.15uF + 0.1uF = 1.25uF

    I thought the LM386 might make a better ultrasonic transducer driver
    than the 555 astable circuit I have but it seems a little messy in
    comparason.

    Regards,

    Andrew.
     
  9. Rubicon

    Rubicon Guest

    Thanks.

    Though mathematics was never my strong suit I can work through that
    formula with the 1kHz/circuit values example to start with.

    Andrew.
     
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