Patent ID: 7208930

Claim:
A bandgap voltage regulator, comprising: an output terminal (VP); a common terminal (COM); a first diode-connected bipolar transistor (Q 1 ) connected between said output terminal and a first node such that it supplies a current to said first node; a first resistor (R 1 ) connected between said first node and a second node; a second resistor (R 2 ) connected between said second node and a third node; a second bipolar transistor (Q 2 ) having an emitter area x, said second bipolar transistor's collector-emitter circuit connected between said third node and said common terminal and its base terminal connected to said second node; a third resistor (R 3 ) connected between the base and emitter of said second bipolar transistor, such that said second bipolar transistor's base-emitter voltage is across said third resistor; a fourth resistor (R 4 ) connected between said first node and a fourth node; a fifth resistor (R 5 ) connected between said fourth node and said common terminal; a third bipolar transistor (Q 3 ) having an emitter area A*x, where A>0, said third bipolar transistor's base connected to said third node, its emitter connected to said common terminal, and its collector connected to said fourth node; and an amplifier arranged to maintain a voltage V out between said output terminal and said common terminal such that the voltages at the base of said second bipolar transistor and the collector of said third bipolar transistor are approximately equal, thereby maintaining the current densities in said second and third bipolar transistors in a fixed ratio such that the difference voltage ΔV BE =V be(Q2) −V be(Q3) across said second resistor, the current in said second resistor, and a component of the currents in said first and fourth resistors are proportional-to-absolute-temperature (PTAT), said second bipolar transistor's base-emitter voltage creating a complementary-to-absolute-temperature (CTAT) current in said third resistor and a component of CTAT current in said first resistor, said resistors sized such that V out is a multiple of V bg , where V bg is the bandgap voltage for the fabrication process used to make the regulator's bipolar transistors, such that V out is temperature invariant, to a first order.