Constant current circuit
View Patent ↗A constant-current circuit comprising: a temperature-compensation circuit to output a temperature-compensated first current; and a current-supply circuit to supply a second current to the temperature-compensation circuit, the temperature-compensation circuit including a voltage-multiplication circuit including a first transistor to generate a base-collector voltage obtained by multiplying a base-emitter voltage by a predetermined ratio, a second transistor identical in conductivity type and substantially equal in base-emitter voltage to the first transistor, a first resistor having two ends connected to a first-transistor collector and second-transistor base, respectively, and a second resistor having two ends connected to first and second-transistor emitters, respectively, the first current being output according to a second-transistor collector current, the second current being supplied to a connection point between a second-transistor base and the first resistor, to generate between both ends of the first resistor a voltage varying substantially in proportion to temperature.
1. A constant current circuit comprising:
a temperature compensation circuit configured to output a first current which is temperature-compensated; and
a current supply circuit configured to supply a second current to the temperature compensation circuit,
the temperature compensation circuit including:
a voltage multiplication circuit including a first transistor configured to generate a base-collector voltage obtained by multiplying a base-emitter voltage by a predetermined ratio;
a second transistor identical in conductivity type and substantially equal in base-emitter voltage to the first transistor;
a first resistor having one end connected to a collector of the first transistor and the other end connected to a base of the second transistor; and
a second resistor having one end connected to an emitter of the first transistor and the other end connected to an emitter of the second transistor,
the first current being output according to a collector current of the second transistor, and
the second current being supplied to a connection point between the base of the second transistor and the first resistor, to generate between both ends of the first resistor a voltage varying substantially in proportion to temperature,
the current supply circuit including:
a third transistor and a fourth transistor whose emitter areas are different from each other; and
a fifth resistor whose temperature coefficient is substantially equal to a temperature coefficient of the first resistor, the fifth resistor having both ends applied with a differential voltage between a base-emitter voltage of the third transistor and a base-emitter voltage of the fourth transistor,
wherein the second current is supplied according to a current flowing through the fifth resistor.
2. A constant current circuit comprising:
a temperature compensation circuit configured to output a first current which is temperature-compensated; and
a current supply circuit configured to supply a second current to the temperature compensation circuit,
the temperature compensation circuit including:
a voltage multiplication circuit including a first transistor configured to generate a base-collector voltage obtained by multiplying a base-emitter voltage by a predetermined ratio;
a second transistor identical in conductivity type and substantially equal in base-emitter voltage to the first transistor;
a first resistor having one end connected to a collector of the first transistor and the other end connected to a base of the second transistor; and
a second resistor having one end connected to an emitter of the first transistor and the other end connected to an emitter of the second transistor;
the first current being output according to a collector current of the second transistor; and
the second current being supplied to a connection point between the base of the second transistor and the first resistor, to generate between both ends of the first resistor a voltage varying substantially in proportion to temperature,
the voltage multiplication circuit including:
a third resistor having one end connected to a base of the first transistor and the other end connected to the collector of the first transistor; and
a fourth resistor whose temperature coefficient is substantially equal to a temperature coefficient of the third resistor, the fourth resistor having one end connected to the base of the first transistor and the other end connected to the emitter of the first transistor,
the current supply circuit including:
a third transistor and a fourth transistor whose emitter areas are different from each other; and
a fifth resistor whose temperature coefficient is substantially equal to a temperature coefficient of the first resistor, the fifth resistor having both ends applied with a differential voltage between a base-emitter voltage of the third transistor and a base-emitter voltage of the fourth transistor,
wherein the second current is supplied according to a current flowing through the fifth resistor.
3. A constant current circuit comprising:
a temperature compensation circuit configured to output a first current which is temperature-compensated; and
a current supply circuit configured to supply a second current to the temperature compensation circuit,
the temperature compensation circuit including:
a voltage multiplication circuit including a first transistor configured to generate a base-collector voltage obtained by multiplying a base-emitter voltage by a predetermined ratio;
a second transistor identical in conductivity type and substantially equal in base-emitter voltage to the first transistor;
a first resistor having one end connected to a collector of the first transistor and the other end connected to a base of the second transistor; and
a second resistor having one end connected to an emitter of the first transistor and the other end connected to an emitter of the second transistor,
the first current being output according to a collector current of the second transistor, and
the second current being supplied to a connection point between the base of the second transistor and the first resistor, to generate between both ends of the first resistor a voltage varying substantially in proportion to temperature,
the current supply circuit including:
a reference voltage generation circuit configured to generate a predetermined temperature-compensated reference voltage;
a fifth transistor having a base applied with the reference voltage; and
a sixth resistor whose temperature coefficient is substantially equal to a temperature coefficient of the first resistor, and through which an emitter current of the fifth transistor flows,
wherein the second current is a collector current of the fifth transistor.
4. A constant current circuit comprising:
a temperature compensation circuit configured to output a first current which is temperature-compensated; and
a current supply circuit configured to supply a second current to the temperature compensation circuit,
the temperature compensation circuit including:
a voltage multiplication circuit including a first transistor configured to generate a base-collector voltage obtained by multiplying a base-emitter voltage by a predetermined ratio;
a second transistor identical in conductivity type and substantially equal in base-emitter voltage to the first transistor;
a first resistor having one end connected to a collector of the first transistor and the other end connected to a base of the second transistor; and
a second resistor having one end connected to an emitter of the first transistor and the other end connected to an emitter of the second transistor,
the first current being output according to a collector current of the second transistor, and
the second current being supplied to a connection point between the base of the second transistor and the first resistor, to generate between both ends of the first resistor a voltage varying substantially in proportion to temperature,
the voltage multiplication circuit including:
a third resistor having one end connected to a base of the first transistor and the other end connected to the collector of the first transistor; and
a fourth resistor whose temperature coefficient is substantially equal to a temperature coefficient of the third resistor, the fourth resistor having one end connected to the base of the first transistor and the other end connected to the emitter of the first transistor,
the current supply circuit including:
a reference voltage generation circuit configured to generate a predetermined temperature-compensated reference voltage;
a fifth transistor having a base applied with the reference voltage; and
a sixth resistor whose temperature coefficient is substantially equal to a temperature coefficient of the first resistor, and through which an emitter current of the fifth transistor flows,
wherein the second current is a collector current of the fifth transistor.