One of the op amps uses +- 12 volts and the other +- 5 volts. With only one circuit, I understand that the common ground for the entire circuit is midway between the two supply voltages, but when the second circuit is present, I do not understand where the common ground is that connects the two circuits.
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simulate this circuit – Schematic created using CircuitLab
Figure 1. The common point of the ±5 V is simply connected to the common point of the ±12 V supply. Usually this is done at the voltage regulators.
You may need to be careful if the output of the higher voltage op-amp is feeding the input of the lower voltage op-amp to ensure that you don't exceed the maximum input voltage.
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simulate this circuit – Schematic created using CircuitLab
Bipolar Supplies have 3 terminals
Op Amps only need two, but the inputs must be somewhere in between defined by the datasheet Vcm limits.
Tony Stewart EE75
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just a small thing, the signs of the voltage should all be the same – BeB00 Jan 30 '21 at 19:17
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did you think I had the wrong polarity shown? – Tony Stewart EE75 Jan 30 '21 at 20:23
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No, the labelling of the voltages is incorrect. If V4 was -5V, then the voltage at the bottom right would be more positive than ground – BeB00 Jan 30 '21 at 20:33
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-5V was meant to indicate the output on the -ve side, sorry for the confusion – Tony Stewart EE75 Jan 30 '21 at 20:43
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Most OPamps are bipolar powered, as such as long as the signal is ground referenced, pick which ever supply provides enough headroom to faithfully reproduce the presented signal. If the gain is set to 10 and the input is 1 volt, you couldn't reasonably pick the +/- 5 volt supply because the output would clip, whereas the +/-12 supply would allow the output to be faithfully reproduced. simply connect Vcc to the + and Vee to the -
