voltage buffer using TL082CP

Discussion in 'General Electronics Chat' started by legolas11, Feb 26, 2013.

  1. legolas11

    Thread Starter Member

    Feb 26, 2013
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    Hi all,
    I am trying to design a simple voltage follower in breadboard using TL082cp opamp and the circuit is attached. However i am getting very noisy output even though the simulator worked fine.
    I have connected everything as in the picture and connected the ground probe of osciloscope to the negative supply. Is there anything that i did wrong here?? is it necessery to use a ground connection here.

    Thnak You
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    TL082 requires a dual supply. If you are going to operate it from a single 10V supply, you will have to create a pseudo ground at +5V and reference all signals to this common reference.
     
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    Also, the TL0xx series opamps can't get within 3v of the negative rail, nor 1.5v of the positive rail. There are many more modern opamps available which are RRIO (rail-to-rail input & output), in the same prrice range.

    Also, you don't show bypass capacitors across the supply pins. They aren't optional.
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Also, no matter what sort of power supply arrangement you use, the -terminal of the function generator needs to be connected to circuit ground.
     
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  5. DangerousBill

    Active Member

    Jul 21, 2010
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    In addition to the issues outlined by others, C3 bothers the hell out of me. Try shorting it.
     
  6. DangerousBill

    Active Member

    Jul 21, 2010
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    I just noticed. Both sides of the signal from the wave generator are floating. There's no hard tie between either signal line and the power supply.
     
  7. legolas11

    Thread Starter Member

    Feb 26, 2013
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    Thanks a lot for all the advice. Based on these i have redrawn the circuit. Please tell me if i have anything wrong now.

    So this means all the negative terminal (plus/minus power supply, function generator) should be connected at the same point (ground) .
    And for ground u mean the connection to earth, right???

    Thanks
     
  8. #12

    Expert

    Nov 30, 2010
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    "Ground" doesn't actually mean planetary earth, most of the time. It just means "common" in this circuit. Looks good except that there is no reason to drive AC current into a capacitor. Some opamps actually fail when you do that.
     
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  9. legolas11

    Thread Starter Member

    Feb 26, 2013
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    problem solved...thanks all...
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    To emphasize what #12 said, it's not solved until you remove C3. Many op amps will oscillate when cap loaded, and in any case it will screw up the frequency response of your voltage follower.
     
  11. legolas11

    Thread Starter Member

    Feb 26, 2013
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    Ya, i removed that too and checked the results with and without it but did not notice any difference.
    Actually the reason to put it there was, i wanted to connect the buffer to an InAmp (ina 129) and so connected a capacitor and resistor (grounded) to the output before leading it to the inamp input terminal. Am i wrong here???
     
  12. #12

    Expert

    Nov 30, 2010
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    The input impedance of the next amp will protect the TL082 from pure capacitive loading.
     
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