Voltage references vary widely in performance; a regulator for a computer power supply may only hold its value to within a few percent of the nominal value, whereas laboratory voltage standards have precisions and stability measured in parts per million.
Laboratory-grade Zener diode secondary solid-state voltage standards used in metrology can be constructed with a drift of about 1 part per million per year.
Zener diodes are also frequently used to provide a reference voltage of moderate stability and accuracy, useful for many electronic devices.
An avalanche diode displays a similar stable voltage over a range of current.
In silicon, this is approximately 1.25 V. Buried-Zener references can provide even lower noise levels, but require higher operating voltages which are not available in many battery-operated devices.