[Question]0 -12V supply for op amp

audioguru said:

No.
The current in the feedback resistors is not reduced by the input of the opamp. The output of the opamp must try to drive the high current in the low value feedback resistors but can't. If the output is +12V then the current in the 720 ohms of feedback resistors is 16.7mA which is too high to be driven from the output of an opamp and therefore the output voltage of the opamp will be reduced.

If you use 720k worth of feedback resistors then when the output is 12V the current in the feedback resistors is only 16.7uA which is easier for the output of the opamp to drive. Then the output of the opamp will be closer to +12V.

The input current of opamps is almost nothing. Some opamps have FET inputs with virtually no input current.

Click to expand...