EL_IN signal varies from 0-12V. The output ADC_EL is going to controllers ADC with 0-3V range.

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Can someone please explain this circuit & if this circuit is correct or not? Should the EL_IN be connected to inverting or non-inverting terminal?

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    \$\begingroup\$ If you're wanting a voltage follower, feed the output back to the inverting terminal. \$\endgroup\$ – Jonathan Wheeler May 1 '16 at 18:29
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    \$\begingroup\$ If you want your output voltage to be 1/4, you want a 3:1 ratio in R89 to R90 \$\endgroup\$ – Jonathan Wheeler May 1 '16 at 18:30
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    \$\begingroup\$ positive loopback aren't admitted. You do amplify and bring back the signal all the time, this goes out of bounds. Swap the +/- inputs. \$\endgroup\$ – Marko Buršič May 1 '16 at 18:33
  • \$\begingroup\$ As a rule of thumb "feedback goes to the negative terminal" \$\endgroup\$ – Sam May 1 '16 at 23:31

You are trying to create a divider with a voltage follower. The inverting and non-inverting inputs need to be swapped.


simulate this circuit – Schematic created using CircuitLab

Figure 1. Passive 4:1 voltage divider.

The circuit of Figure 1 should do the trick for you.

  • R1,2 and 3 can be replaced by any combination of resistors to give you three times the value of R4.
  • R4 needs to be a factor of ten lower than the input impedence of your 0 - 3 V ADC so that the ADC doesn't load the divider too much.
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