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I'm working on one OP07CD circuit, Application - this amplifier circuit used for amplification pressure sensor circuit & feeding output to microcontroller ADC input pin. Problem Statement - Getting offset voltage up to +10mv at output. Observation - Even connecting input pin to GND, still OPAMP output is 10 mv observed. I'm trying to finding exact equivalent Op Amp which having better noise rejection ratio, lowest offset. Can anyone help me for how can I select? Please suggest. enter image description here

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The TI OP07D has a maximum unadjusted input offset voltage of +/-150uV, so with a gain of about 2 you should not have more than about +/-300uV output offset. That's with no 20kΩ trimpot. Higher grade versions of the OP07D than the cheapest 'D' version have lower maximum offset.

Of course, with the trimpot you likely can get at least several mV adjustment range plus and minus, so you should be able to null it out. If you cannot, my guesses are:

  1. The trimpot is connected incorrectly (eg. the wiper goes to 1 or 8 rather than V+). I think this is most likely.

OR

  1. The OP07 is actually something else.

There's nothing major wrong with your circuit (a bit higher resistor values would be better and it would be good to make R184 at least approximately equal to R181||R182, but for sure neither of those things are causing your problem.

A third possibility would be some kind of high current flowing through your ground that means that there is a potential between the 'bottom' of R184 and your grounded input. If you've got something not shown in the schematic (like a capacitor) connected to the output then it also could be oscillating which could look like a DC offset if you are not using an oscilloscope.

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  • \$\begingroup\$ Thanks for the advice, Im thinking to replace OP07 with TLV07, will this work? \$\endgroup\$ Commented Jul 28, 2023 at 5:17
  • \$\begingroup\$ If it doesn't work with an actual OP07 it's unlikely to work with another part unless you accidentally fix whatever is wrong. So I suggest getting to the bottom of it rather than just randomly changing things. \$\endgroup\$ Commented Jul 28, 2023 at 5:21
  • \$\begingroup\$ The OP07 differs from other devices in the connection of the offset trimpot to V+ instead of V-like the 741. So that's not the problem, but the trimpot should be able get 0V output. \$\endgroup\$
    – PStechPaul
    Commented Jul 28, 2023 at 5:21
  • \$\begingroup\$ The TLV07 lacks offset adjust so if the trimpot is wired incorrectly or correctly it will be ignored. \$\endgroup\$ Commented Jul 28, 2023 at 5:53
  • \$\begingroup\$ It might also be worth checking you're not accidently loading GPIO P1.5 and creating a voltage drop across R182. This can be done easily by comparing voltages on pin 6 and GPIO P1.5 \$\endgroup\$
    – Hyp
    Commented Jul 28, 2023 at 5:57

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