Making a precision voltage source is easy, but not so easy if the voltage should be consistent over wide range of ambient temperature. Such requirement might be needed in high precision measurement system, for providing reference voltage in analog to digital conversion for example. Here is the circuit’s schematic diagram:

Precision power regulator with low temperature coefficient circuit schematic

The LM236, LM336 voltage references are easier to use than zener diodes. Their low impedance and wide current range facilitate biasing in any circuits. Besides, the breakdown voltage or the temperature coefficient can be adjusted so as to optimize the performance of the circuit. [Source: STMicroelectronics Application Note]