Patent ID: 8330445

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; a plurality of switches configured to selectively change how at least some of the X transistors are connected within the circuit; a first base-emitter voltage branch configured to provide a first amount of current to the current path of each transistor within the first base-emitter voltage branch to produce a first base-emitter voltage (VBE 1 ); a second base-emitter voltage branch configured to provide a second amount of current to the current path of each transistor within the second base-emitter voltage branch to produce a second base-emitter voltage (VBE 2 ), where the second amount of current is less than the first amount of current; a first current preconditioning branch configured to provide a current substantially equal to the first amount of current to each transistor within the first current preconditioning branch; and a second current preconditioning branch configured to provide a current substantially equal to the second amount of current to each transistor within the second current preconditioning branch; wherein the VPTAT is produced based on the first base-emitter voltage (VBE 1 ) and the second base-emitter voltage (VBE 2 ), which are produced, respectively, by the first base-emitter voltage branch and the second base-emitter voltage branch; wherein the transistors within the first and second preconditioning branches are not used to produce VBE 1 and VBE 2 ; and wherein the switches are used to selectively change over time which of the X transistors are in the first base-emitter voltage branch, the second base-emitter voltage branch, the first current preconditioning branch, and the second current preconditioning branch.