Patent ID: 7852062

Claim:
A reference current generating apparatus for generating a reference current, comprising: a first constant current generator including a first current source transistor and a first diode connected to each other at a first connection node, a second current source transistor and a first resistor connected to each other at a second connection node, a second diode and the first resistor connected to each other at a third connection node, the second diode having a current capacity larger than a current capacity of the first diode, the first connection node and the second connection node respectively connected to inputs of a first differential amplifier that maintains the first and second connection nodes at an identical electric potential, gates of the first and second current source transistors connected to an output of the first differential amplifier, a transistor connected to the output of the first differential amplifier and that turns on the first and second current source transistors at a time when a power supply is turned on, and a third current source transistor connected to a second transistor by a fourth connection node and that biases the first differential amplifier via the fourth connection node; a second constant current generator including a second differential amplifier having inputs, the third connection node connected to one of the inputs of the second differential amplifier, a fourth current source transistor and a second resistor connected to each other at a fifth connection node, the second resistor having a plurality of voltage dividing resistors connected in series to each other by dividing nodes, a voltage of a selected one of the dividing nodes of the second resistor being applied to another of the inputs of the second differential amplifier, gates of the fourth current source transistor and a fifth current source transistor are connected to an output of the second differential amplifier, a third transistor connected to the output of the second differential amplifier that turns on the fourth current source transistor, the second transistor and a plurality of transistors forming a first current mirror connected to the fifth connection node via respective selected ones of the plurality of transistors to turn on the fourth current source transistor at the time when the power supply is turned on, and the fifth current source transistor connected to a fourth transistor by a sixth connection node and that biases the second differential amplifier via the sixth; and an output circuit including a sixth current source transistor connected to the output of the second differential amplifier, a seventh connection node between the sixth current source transistor and a third resistor providing a first reference output, and the fourth transistor and a fifth transistor connected to each other and forming a second current mirror, and an eighth connection node between the fifth transistor and a fourth resistor providing a second reference output.