Patent ID: 6570438
Filing Date: 2003-05-27
Classification: G05F

Abstract:
A PTAT reference comprising:first, second, third and fourth transistors, each having an emitter, a base and a collector for conducting current through the respective transistor between its emitter and its collector, the base emitter voltage of each transistor being responsive to the collector current in the respective transistor, the base currents of the transistors being non-zero when the transistors are conducting; an input current; the first transistor having its base coupled through a first resistor to the collector of the first transistor and through the first resistor to the base of the fourth transistor; the emitter of the first transistor being coupled to the base of the third transistor and to the collector of the second transistor; the third transistor having its emitter coupled through a second resistor to the emitter of the second transistor and its collector coupled to the emitter of the fourth transistor and to the base of the second transistor; the input current being coupled to supply current through the first and second transistors, and the second resistor and the third and fourth transistors; at least one of the transistors being a different size from the other transistors so that a voltage across the second resistor is responsive to the difference in base emitter voltages of the second and fourth transistors and the first and third transistors; the first resistor being selected to reduce the variation in the current in the collector of the fourth transistor with variations in the current provided by the input current.