A simple discrete regulator circuit using Zetex voltage references and transistors can realize performance levels that are beyond IC regulators, whilst being of reasonable cost and with very little board space overhead.
Although Integrated Circuit (IC) regulators dominate the marketplace through their combination of simplicity and low cost, there are situations where lower noise and better regulation are requirements for the highest level of circuit performance. In applications where performance is critical and efficiency and cost may be of a lower priority, such as data conversion in audio and video, instrumentation and low noise power for clock circuits, this discrete circuit can be immensely useful.

Precision voltage regulation for ultra-low noise applications ->>> LINK <<<