ABSTRACT
Opamps in general have very good power supply rejection ratios (PSRR). PSRR is typically frequency dependent and different for the +V and -V supply pins. Fortunately even the cheapest Integrated Circuit (IC) regulators like the classic 78xx/79xx series have low enough noise and ripple outputs that opamp PSRR performance is rarely an issue. The 78/79 series with transistor voltage-setting remains the most cost-effective way to make a non-standard-voltage power supply at the time of writing. Intelligent placing of the decouplers can help—putting them near where the ground and supply rails come onto the Printed Circuit Board (PCB) means that ripple will go straight back to the power supply without flowing through the ground tracks on the rest of the PCB. One of the main reasons for using discrete audio electronics is the possibility of handling larger signals than can be coped with by opamps running off ±17 V rails.
