Patent ID: 6265857
Filing Date: 2001-07-24
Classification: G05F,Y10S

Abstract:
A constant current source circuit, comprising:a first current source having a positive coefficient of temperature compensation to generate a first bias voltage connected to a first voltage-controlled current source;a second current source having a negative coefficient of temperature compensation to generate a second bias voltage connected to a second voltage-controlled current source;a first current selector comprising at least two transistors; the source/emitter of a first and a second transistor connected to the first voltage-controlled current source; the gate/base of the first transistor connected to a bandgap reference voltage and the drain/collector of the first transistor connected to a constant voltage; the gate/base of the second transistor connected to a variable control voltage;a second current selector comprising at least two transistors, the source/emitter of a third and fourth transistors connected to the second voltage-controlled current source; the gate/base of the third transistor connected to the bandgap reference voltage, the drain/collector of the third transistor connected to the drain/collector of the second transistor; the gate/base of the fourth transistor connected to the variable control voltage, and the drain/collector of the fourth transistor connected to the constant voltage;an output current derived from selectively combining current from the second and third transistors of the first and second current selectors, respectively.