Reference current source
A reference current source 100 includes a reference voltage circuit 110 , generating a reference voltage Vref; a voltage division circuit 130 , dividing the reference voltage Vref and outputting a divided voltage Vdiv; and an output MOS transistor 140 , supplying a reference current Iref in response to the divided voltage Vdiv being applied to a gate terminal 140 G. The reference voltage circuit 110 includes a depletion type MOS transistor 111 , and an enhancement type MOS transistor 112 having same conductivity type and impurity concentration as a channel 111 c of the depletion type MOS transistor 111 and a different Fermi level from a gate electrode 111 g of the depletion type MOS transistor 111 . The voltage division circuit 130 outputs the divided voltage Vdiv within a voltage range which is 0V or above and lower than a cross point X to the gate terminal 140 G of the output MOS transistor 140.
1 . A reference current source, comprising:
a reference voltage circuit, generating a reference voltage;
a buffer amplifier including an output terminal and a non-inverting input terminal connecting to the reference voltage circuit to receive the reference voltage;
a voltage division circuit, connecting to the output terminal of the buffer amplifier and dividing the reference voltage and outputting a divided voltage; and
an output MOS transistor, supplying a reference current in response to the divided voltage being applied to a gate terminal,
wherein the reference voltage circuit comprises:
a depletion type MOS transistor; and
an enhancement type MOS transistor, having same conductivity type and impurity concentration as a channel of the depletion type MOS transistor and a different Fermi level from a gate electrode of the depletion type MOS transistor,
wherein the voltage division circuit outputs the divided voltage to a gate terminal of the output MOS transistor, wherein the divided voltage is within a voltage range which is above OV and lower than a cross point at which a gate voltage-drain current characteristic of the output MOS transistor does not depend on temperature in order that a positive temperature coefficient of a drain current of the output MOS transistor cancels a negative temperature coefficient of the reference voltage, wherein the divided voltage cancels a temperature characteristic of the reference voltage so that the drain current of the output MOS transistor does not fluctuate with temperature.
2 . The reference current source according to claim 1 , wherein the voltage division circuit comprises a trimming circuit capable of adjusting the divided voltage.