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  1. Oct 24, 2009 #1
    ORCAD PSPICE : LM324 Help !!

    I am making a simulation of my project on Intercom using LM324 opamp as preamp and before Power amp ckt.

    But I am having trouble with that.

    I tried making an inverter using LM324 with pin 11 as ground. But this does not give correct result. Although the datasheet shows that pin 4 is +Vcc and pin 11 is GND.

    The tutorials I could find on internet used a negative supply at pin 11 though it should have been ground.

    Please help.
  2. jcsd
  3. Oct 24, 2009 #2


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    Staff: Mentor

    Re: ORCAD PSPICE : LM324 Help !!

    Pin 11 is GND for single-supply operation, but you can also use the LM324 opamp in split supply operation, in which case pin 11 will be V-.

    http://www.national.com/ds/LM/LM124.pdf [Broken]

    Why are you trying to make an "inverter" with an opamp? Do you mean inverting amplifier? You will not have much luck making an inverting amplifier with a single-supply opamp, because your output would try to be below GND, and well, the opamp is not running between split supplies, eh?

    To use a single supply opamp in an inverting amplifier configuration, you will need to bias the input and output up somehow and capacitively couple your input signal in, so that both can run above GND.
    Last edited by a moderator: May 4, 2017
  4. Oct 24, 2009 #3
    Re: ORCAD PSPICE : LM324 Help !!

    Got the Inverting thing.....but could you please explain the single supply operationa and split supply operation?
    Does split supply operation mean using symmetric and opposite power supplies as +V and -V?

    and one more thing.....can the Vdc used here be directly used...I mean connect one end of Vdc to pin 4 and other to GND and use another Vdc connect negative terminal to pin 11 and positive to GND?
  5. Oct 24, 2009 #4


    User Avatar

    Staff: Mentor

    Re: ORCAD PSPICE : LM324 Help !!

    Split supplies just means some +V and some -V. Usually they are symmetric, but they don't have to be. You might use +12V and -5V, for example.

    Sorry, I'm not understanding the 2nd part of your question.
  6. Oct 24, 2009 #5
    Re: ORCAD PSPICE : LM324 Help !!

    got it running thanks.....nevermind for the second question... am having trouble with the simulation of intercom...will be asking as new problems crop up.

    Could you explain how to use center tap transformer in PSPICE and a bridge rectifier.
    I have to step down 330V ac to LM324 range (30V) so what should be the values of L1 and L2 in secondary in PSPICE? 330:30 gives 11. Using 20mH Lp should L1 and L2 be 166uH?

    Also PSPICE does not simulate components outside its library...like a Center tap is available as discreet and a bridge also in the discreet library.....but the Simulation omits them.
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