Patent ID: 7075281
Filing Date: 2006-07-11
Classification: G05F,Y10S

Abstract:
1. A current source circuit providing an output current being proportional to absolute temperature, the circuit comprising: a first transistor and a first resistor connected in series between a positive power supply voltage and a ground voltage, the first transistor having a control terminal coupled to a first voltage related to a current proportional to absolute temperature to cause a current proportional to absolute temperature to flow through the first transistor and the first resistor, a second voltage being a voltage proportional to absolute temperature being developed at a first node between the first transistor and the first resistor; a first voltage-current buffering circuit having a first terminal coupled to receive the second voltage, a second terminal providing a third voltage being a buffered voltage of the second voltage, and a third terminal providing the output current proportional to absolute temperature, the output current being equal to a current flowing in the second terminal; a first voltage controlled resistive device having a first terminal coupled to the second terminal of the first voltage-current buffering circuit, a second terminal coupled to the ground voltage and a voltage control terminal receiving a control voltage; a constant voltage circuit receiving a bandgap voltage as an input voltage at an input terminal, the constant voltage circuit comprising an output stage providing a fourth voltage being a buffered voltage of a fifth voltage related to the bandgap voltage at a first output terminal and providing a second output current at a second output terminal; a second voltage controlled resistive device having a first terminal coupled to the first output terminal of the constant voltage circuit, a second terminal coupled to the ground voltage and a voltage control terminal receiving the control voltage, the second voltage controlled resistive device matching the first voltage controlled resistive device; a first current mirror mirroring the second output current of the constant voltage circuit and supplying the mirrored current to a second resistor; a third resistor matching the second resistor and being supplied by a first constant current; and a comparator receiving a voltage across the second resistor and a voltage across the third resistor, the comparator generating the control voltage for controlling the resistance of the first and second voltage controlled resistive devices, the control voltage being generated to force the voltage across the second resistor to equal to the voltage across the third resistor.