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LM324: About the supporting circuit's difference between LM324 and TL084

user4917449
Intellectual 875 points
Part Number: LM324
Other Parts Discussed in Thread: TL084

Hi TI,

Is there any difference between LM324's supporting circuit and TL084's supporting circuit? Now I want to use the LM324 instead of TL084 because of the battery voltage. However, the zero point of LM324 is not good, because LM324 has more obvious noise than TL084.

How can I eliminate the noise? Is there any application schematic which can display the difference between LM324 and TL084?

Thanks

  • 0
    TI__Genius 13445 points
    User,

    We don't have a specific application schematic that directly displays the difference between the 2 devices. But if you can tell me more about you're trying to achieve and your application, I can help recommend a certain topology where each device may be suitable.

    What is the battery voltage? What kind of signal are trying to drive? What is the load? Are there any key care about beside noise?
    We can mitigate noise level on your circuit by recommending a low noise op amp as a starting point.

    Please provide me with those details and I will gladly help you move forward with your design.

    Regards,

    -Mamadou
  • 0 in reply to Mamadou Diallo
    Intellectual 875 points

    Thanks for help.

    1.The battery voltage ranges from 4.2v to 3.6v. Besides, I use a MAX860 DC-DC converter (it’s not a TI’s product) to output the +-2.7v, to drive the LM324. (+-2.7v cannot drive the TL084 because the recommended voltage is +-5v at least)

    2.I’m collecting the EMG (kind of electronic signal of muscle) , and I’m using the LM324 to convert it to the voltage range which CC2640R2 can accept. When the muscle is totally relaxing, the output voltage must be 0. However, actually it’s not 0, and there is some noise.

    (P.S. Both the TL084 and LM324 are TSSOP-14 layout. Cannot use other layouts)


    Thanks.

  • 0 in reply to user4917449
    Guru 140200 points
    Hi,

    the LM324 and the TL084 are totally different OPAmps. Can you show us a schematic of your circuit?

    Kai
  • 0 in reply to kai klaas69
    TI__Guru*** 140136 points

    User,

    Both datasheets show a device schematic. Zero point noise is a vague term. I think that means "zero crossing" distortion. LM324 does have a time delay when switching between sourcing (darlington NPN) and sinking current  (PNP follower).

    Does your noise look like waveform "B"? The solution is to make sure the current only flows through the NPN Darlington (sourcing) or PNP follower (sinking) driver but not both.  

  • 0 in reply to kai klaas69
    Intellectual 875 points
    Thanks all the same, but my company is afraid of schematic being pirated...
  • 0 in reply to Ron Michallick
    Intellectual 875 points
    Thanks a lot for the testing schematic.

    Actually, "The Zero Point", I mean, although no electronic signal is input, the output is still not zero. Is there any method to eliminate the noise?
  • 0 in reply to user4917449
    Guru 140200 points
    Hi,

    can you post a scope plot of this "zero point noise"?

    Kai