square wave

Discussion in 'The Projects Forum' started by kahafeez, Jan 20, 2009.

  1. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
    150
    0
    Hi all, i need to generate a pure square wave of 0V lo and 5V high of abt 2.5KHz...... i tried this circuit and it gave me a square wave of abt 0.5 or may be 1V lo..... i need a wave that has exactly 0V as lo..... 5V at hi is nt necessary it can be 3V or watever bt there has be be 0V as lo..... plz suggest a schematic
     
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  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    What do you want to drive and you need exactly 0V?
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Just select a resistor for R1 that is on the small side compared to R2. The greater the ratio, the better the duty cycle.

    For example, a 75KΩ and 1KΩ resistor set will produce a 50.33% duty cycle.

    [​IMG]
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    A BJT 555 will not get to 0v output.
    A CMOS 555 might get near 0v output, but not quite there.

    If you need precisely 0v output, you're going to have to tell us a lot more about your load requirement. Right now, we don't know anything about your load.
     
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