Patent ID: 7812649

Claim:
An apparatus comprising: a first voltage rail; a second voltage rail; a first bipolar transistor that is coupled to the second voltage rail at its emitter, wherein the first bipolar transistor is diode-connected; a plurality of resistor that are coupled in series with one another between the first voltage rail and the collector of the first bipolar transistor, wherein the sum of the base-emitter voltage of the first bipolar transistor and the voltage drop across the plurality of resistor is equal to a bandgap voltage; a current mirror that is coupled to the first voltage rail; a second bipolar transistor that is coupled to the current mirror at its collector and to the second voltage rail at its emitter, wherein the second bipolar transistor has a first emitter area; and a third bipolar transistor that is coupled to the current mirror at its collector and to the second voltage rail at its emitter, wherein the third bipolar transistor has a second emitter area, wherein the bases of the second and third bipolar transistors are coupled across at least one of the resistors of the plurality of resistor, and wherein the first emitter area, the second emitter area, and the resistances of the plurality of resistors are dimensioned so as to have generally equal collector currents for the second and third bipolar transistors at room temperature.