A temperature compensated voltage reference is created from an operational
amplifier circuit having two substantially identical P-channel metal
oxide semiconductor (P-MOS) transistors with each one having a different
gate dopant. The different gate dopants result in different threshold
voltages for each of the two otherwise substantially identical P-MOS
transistors. The difference between these two threshold voltages is then
used to create the voltage reference equal to the difference. The two
P-MOS transistors are configured as a differential pair in the
operational amplifier circuit and the output of the operational amplifier
is used as the voltage reference. The transistor widths of two P-MOS
transistors are adjusted to minimize voltage variation over a temperature
range.