A bandgap voltage regulator is arranged such that, when a desired output
voltage is present between its output and common terminals, current
densities in a pair of bipolar transistors having unequal emitter areas
are maintained in a fixed ratio. The difference in the transistors'
base-emitter voltages is across a resistor, which thus conducts a PTAT
current. The regulator also generates a CTAT current, and both the PTAT
and CTAT currents are made to flow in another resistor, with the
resulting voltages added by superposition. The regulator's resistors are
sized such that V.sub.out is an integral or fractional multiple of
V.sub.bg, where V.sub.bg is the bandgap voltage for the fabrication
process used to make the regulator's transistors, such that V.sub.out is
temperature invariant, to a first order. The resistors are preferably
realized using unit resistors having a predetermined resistance, or
series and/or parallel combinations of unit resistors.