Patent ID: 7880459

Claim:
A circuit to generate a voltage proportional to absolute temperature (VPTAT), comprising: a group of X transistors, each of which includes a base and a current path between a collector and an emitter; wherein a first subgroup of Y of the X transistors are used to produce a first base-emitter voltage (VBE 1 ) indicative of a voltage drop between the base(s) of the Y of the X transistors and the emitter(s) of the Y of the X transistors, where 1≦Y<X; wherein a second subgroup of Z of the X transistors are used to produce a second base-emitter voltage (VBE 2 ) indicative of a voltage drop between the bases of the Z of the X transistors and the emitters of the Z of the X transistors, where Y<Z<X; wherein the VPTAT is produced by determining a difference between the first base-emitter voltage (VBE 1 ) and the second base-emitter voltage (VBE 2 ); and wherein which Y of the X transistors are in the first subgroup and used to produce the first base-emitter voltage (VBE 1 ), and which Z of the X transistors are in the second subgroup and used to produce the second base-emitter voltage (VBE 2 ), selectively changes over time.