# Make good use of an unused opamp

If you end up not using one of the opamps in a dual or quad opamp, you can use it to provide the bias needed in single-supply opamp applications (otherwise you should configure it correctly like I described here).

This is a circuit I have used sometimes to provide a stable, low-impedance mid-supply voltage for biasing.

For example values can be: R1 = R2 = 100k and C1 = 0.1uF. If you don’t want Vbias to be half of Vs, you use the following formula:

$$V_{bias} = \frac{R2}{R1 + R2} * V_s$$