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Unity gain buffer

  1. Nov 4, 2014 #1
    Hello,

    Here need a suggestion on Unity gain buffer using op-amp 741.

    The output i need in the range according to change in LVDT sensor (resistive type).
    The output of the sensor is 35mv to 3.5 VDC.
    The circuit i build using op-amp741 as voltage follower where the output is given feedback to non-inverting input.
    Now the output from Op-amp am getting is 1.85 VDC to 3.5VDC.

    The required output is according to the change in LVDT sensor(resistive type) i.e from some mV to 3.5 VDC.
    How can i minimize the voltage of 1.85 VDC at the op-amp ouptut?

    Best Regards.
     
  2. jcsd
  3. Nov 4, 2014 #2

    davenn

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    if you are not running the op-amp off a split rail supply, you wont get the output below ~ 2V

    as an aside, why are you using such an old op-amp ? there are many better newer devices

    Dave
     
  4. Nov 4, 2014 #3
    Thank you for yur reply Dave.
    I don't understand split rail supply.

    I don't have any other components than Op-Amp right now.
     
  5. Nov 4, 2014 #4
    Ok. Is there any circuit for making split voltage (negative voltage)??
     
  6. Nov 4, 2014 #5

    davenn

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    OK here's one example of a split rail PSU

    12V DUAL POWER SUPPLY.jpg

    depending on your overall circuit, you may be able to use a +5V 0V -5V supply

    NOTE ... I don't know where your are in the world, nor your mains voltage, use the appropriate transformer. Also if you only need a + and - 5V the transformer output could also be lower say 9-0-9VAC

    Dave
     
  7. Nov 4, 2014 #6
    Yes, a resistive voltage divider being the simplest one.
     
  8. Nov 4, 2014 #7

    davenn

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    as long as the overall circuit current requirements are very low, that's OK

    since we don't know the full extent of what the OP is doing, I didn't suggest that method

    Dave
     
  9. Nov 4, 2014 #8

    jim hardy

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    Two batteries can make a split supply.

    LM324 can work from a single (not split) supply .
     
  10. Nov 4, 2014 #9
    Thank you dear all for your best suggestions.

    I have used CENTER-TAPPED BATTERY CIRCUIT for split rail voltages for Op-Amp 741.
    The output is exactly as what i needed. That changes according to LVDT sensor.

    Best Luck.
     

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