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I am designing the following circuit shown in the atached image. It is a wheatsone bridge with the differential output attached to voltage followers on each terminal and then connected to a single amplifier with a gain of 10. In LTSpice simulation it works as expected. When building the circuit physically on a breadboard, the wheatstone bridge differential output is the 205mV as expected, but when it is connected to the rest of the circuit the differential output drops down to around 100mV for both the bridge's differential output Vo+ - Vo- and for the buffer outputs V1-V2.

What could be causing this? The opamps used are UA741CM

screenshot of LTSpice simulation of the circuit

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  • \$\begingroup\$ Breadboards are not the most reliable platform for this type of experiment. \$\endgroup\$
    – Fredled
    Nov 2, 2023 at 21:35

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Those op-amps need to be powered from +/-9V for this to work - at minimum. Ideally +/-12V. Or use better op-amps that don’t need such wide supplies to work.

The op-amps you’re using must have common mode range down to ground since that’s what you’re feeding them, if you want to use a single supply.

Modern low cost rail to rail input/output op amps will do the trick. 741 is not terrible but it really was designed for symmetric supplies - typically +/-15V for +/-10V output range.

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The input resistance of the 741CM is typically 2MΩ but could be as low as 300kΩ which is the same range as the bridge resistors so the loading effect is not insignificant. Either make your bridge resistors smaller or if that's not possible, use a different opamp with higher input resistance, perhaps a JFET input.

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