Need help getting at least +/-10 V from op-amp
The circuit is bogus.

The opamp and its four resistors have the general form of a difference amplifier. Since VOUT can never be greater than VDD, it's simply impossible for the output of the opamp to ever be greater than VDD, no matter what you do with the resistor values.

At a minimum, you'd have to add a resistor between the opamp "&ndash;" input and ground, in order to create the required offset. If you make this resistor equal to R1, then the effective reference voltage will be VDD/2 &mdash; the middle of the range of VOUT. This means that the differential input voltage (between VOUT and VDD/2) can range between -2.5V and +2.5V.

Then, R3 should be half this value. In order to get a &plusmn;10V output range (from a differential input of &plusmn;2.5V) you need a gain of 4, so R2 and R4 should be 4&times; the value of R3 (i.e., 2&times; the value of R1).







simulate this circuit &ndash; Schematic created using CircuitLab