square oscillator

Discussion in 'General Electronics Chat' started by fourty, Feb 2, 2014.

  1. fourty

    Thread Starter New Member

    Oct 13, 2013
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    SO.png


    the circuit didn't work in multisim plz someone can help me? i can't found the problem
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    The signal can not go below ground.
    If you would feed the LM741 with + and - 6 Volts, the circuit would work.

    Bertus
     
  3. LvW

    Active Member

    Jun 13, 2013
    674
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    Normally, opamps are used with double supply because they are designed for such applications. However, they can be used, of course, with one single supply voltage only - however, in this case, some special provisions/circuitry is necessary for proper biasing.
    Fourty, my recommendation is that you become familiar with both supply alternatives.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,774
    1,103
    Here's how you could configure the circuit.
    N.b. you won't get a good square wave using a 741; it's bandwidth is too limited (as evidenced by the sloping flanks of the waveform shown).
     
  5. LvW

    Active Member

    Jun 13, 2013
    674
    100
    To me more specific: It is the bad 741 slew rate (0.5V/µs) which causes the sloping flanks.
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Also, the 741 is not rail-to-rail on the output pin, so the output stops short of going to 12V and 0V. The reduced amplitude output also effects the trip points at the inverting input, so indirectly effects the frequency as well. All-in-all, the 741 is about the worst opamp you can use for a circuit like this.
     
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