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  • TI Thinks Resolved

TINA/Spice/LM324: LM324

Part Number: LM324

Tool/software: TINA-TI or Spice Models

Hi

I am using LM324 for 10KHz triangle wave generator , I designed circuit is bellow.  but that model not showing proper results. results also below attached .Is it wrong in model or circuit ? 

furthermore clarify  Gain-bandwidth product of LM324 is 1 MHZ . is it sufficient this design or is it need hi speed compactor ? 

  • I think first thing first, I didn't see any voltage generator in your schematic. In real life, an oscillator will have random energy that can hit it and create self sustaining oscillation. However, in ideal simulator, we need to provide that first impulse so that the circuit can start somewhere. Most likely you can use unit step or pulse voltage generator connected to a switch to certain node within your circuit. The switch is "ON" first, then after sometimes turns it off.

    Once you figure that one out, you can also try to replace the LM324 with ideal opamp (VCVS with gain of 1k for instance and put certain GBW such as wide 1MHz to 1GHz) to experiment with the impact between GBW and the result you desire.
  • In reply to Herman Theodorus:

    thank your reply.

    I change lm324 to tl081. it is working without kik off voltage @ t=0. but i face another issue when design  sine generator & simulate both at same time , sine is not coming). when  simulate separately it is working. how rectify this issue 

    circuit

    both circuit simulate @same time

    only sine wave genarator

  • In reply to sa kal:

    I think without solid kick off voltage at t=0, you let simulation engine to randomly pick it's own solution. If it converges to a solution where it provides initial small signal somewhere that then the circuit can amplify using its positive feedback gain, then it's great. But, if it does not converge into that scenario, then it will show nothing.

    All being said, you can try the following:
    1. Try to play around with Analysis -> Analysis Parameters -> TR Maximum Step.
    Perhaps set this parameter to something closer to reasonable samples per cycle of your sine generator.
    I am hoping this way, hopefully the simulator will be able to trap a solution if the Tmax is bounded.

    2. If #1 does not work, I would recommend to try using kick off voltage at t=0 to see if it helps.
  • In reply to Herman Theodorus:

    i try with below circuit with kik off voltage but not getting required outputs

     circuit

    outputs

  • In reply to sa kal:

    While I am not 100% sure, perhaps try the following:

    1. The kick off voltage
    a. Try to move it around the nodes within your schematic to see if there is a sweet spot by which you can trigger it. I suspect it will work better when the node is high impedance node
    b. Try to vary the magnitude of the kick off voltage as well as the rise time/fall time

    2. There could be a chance also you might be able to trigger something when the power supply is ramped up slowly in conjunction with step #1.

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