A bandgap reference generation circuit utilizes two feedback loops to
maintain the voltage at across the current sources to be essentially the
same, such that the reference voltage remains constant over variations in
process, temperature, and supply voltage. The accuracy of the reference
voltage is maintained even at low supply voltages. Furthermore, the
feedback loops increase the output impedance of the current sources,
reducing the amount of noise coupling from the power supply, improving
power supply rejection ratio.