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I'm using the following circuit:

enter image description here

The LM358P is a two-channel operational amplifier. Whatever input voltage I give, I always have 0V at the output of the first op-amp (output from LM358P). In order for the same voltage to appear as at the input, I need to remove the feedback loop in the LM358P_2.

Can someone explain to me why this is happening?

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  • \$\begingroup\$ BTW, the circuit diagram consistently mis-labels those opamps as a LM385. \$\endgroup\$
    – Dan Mašek
    Jul 23, 2023 at 11:38
  • \$\begingroup\$ ?? i dont understand \$\endgroup\$
    – lukassk
    Jul 23, 2023 at 12:32

1 Answer 1

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You are applying +15V to both power supply pins, so the amplifiers cannot work.

Either reverse the grounding/output of the V- source, or change the voltage to +15 to fix it.

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    \$\begingroup\$ Good catch! I missed the -15 as the voltage on V2. \$\endgroup\$ Jul 22, 2023 at 23:15
  • \$\begingroup\$ no matter if I use unipolar or bipolar as you indicated, the same thing happens. This circuit worked properply, but one day after this situation has arisen, all the elements are replaced with new ones, so it's not their fault \$\endgroup\$
    – lukassk
    Jul 23, 2023 at 9:25

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