square wave generator

Discussion in 'Analog & Mixed-Signal Design' started by sean96, Nov 7, 2018.

  1. sean96

    Thread Starter New Member

    Nov 5, 2018
    12
    0
    hello, im a absolute beginner to electronics and i would like some help with this circuit. it is a sqaure wave generator using the lm741C. and im using the triangular output with peak to peak value of 8 v and 100 hz of a function generator. i know that the opamp is functioning as a comparator in this situation but i would like to how is varying the potentiometer over a wide range changing the output duty cycle? (detailed explanation if it's possible. i would really appreciate it. opamp741.PNG
     
  2. MrChips

    Moderator

    Oct 2, 2009
    17,137
    5,296
    This is not a square-wave generator.
    XFG1 is set up as a triangular wave generator.
    R1 is a voltage divider that allows you to select a threshold voltage between -15V and 15V (see green dashed line below). This is used as the reference input to an analog comparator circuit implemented using a 741 opamp. The reference voltage input determines when the output of the comparator is to be LOW or HIGH when the triangular waveform (same as for sine wave shown) is above or below this reference voltage.

    [​IMG]
     
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  3. sean96

    Thread Starter New Member

    Nov 5, 2018
    12
    0
    thanks. i already know how it works now
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    987
    I redrew your circuit, it is became more clear to see, and I also changed R1 to VR1(Variable Resistor), or you can name it as Pot1 (Potentiometer), R6 changed to R1, whatever what kind of components they are that they always have a continuing number sequence, and the polarity of C2 was reversed (I already modified), the Ground is on a middle voltage level when you are using a dual power supply and the -Vee is a more lower voltage level comparing with Ground, a component reversed polarity may damaged soon in a real world.

    R1 change duty cycle_opamp741_sean96.PNG
     
  5. MrChips

    Moderator

    Oct 2, 2009
    17,137
    5,296
    Good eye by @ScottWang for spotting C2 incorrectly connected.
     
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