Drive circuit of light emitting element

A drive circuit of a light emitting element, comprising:

• a differential output circuit which comprises first and second transistors each having a control terminal and first and second terminals, and the first terminals connected to each other and a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second terminal of the second transistor is connected to a power supply voltage source;
• an input circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a dummy circuit for generating a comparison voltage having substantially the same value as the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit upon receipt of the supplied drive voltage;
• a comparison circuit which compares the comparison voltage generated by the dummy circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage supply circuit which generates a voltage in accordance with the level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit and the dummy circuit.

A drive circuit of a light emitting element comprising:

• a differential output circuit which comprises first and second transistors each having a control terminal and first and second terminals, and can adjust the amounts of current flowing between the first and second terminals in accordance with the level of a signal supplied to the control terminals, and the first terminals connected to each other and which comprises a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second terminal of the second transistor is connected to a power supply voltage source;
• an input-circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a comparison circuit which compares the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage supply circuit which generates a voltage in accordance with the input level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit.

A drive circuit of a light emitting element, comprising:

• a differential output circuit which comprises first and second transistors each having a control terminal and first and second terminals, and can adjust the amounts of current flowing between the first and second terminals in accordance with the level of a signal supplied to the control terminals, and the first terminals connected to each other and which comprises a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second terminal of the second transistor is connected to a power supply voltage source;
• an input circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a dummy circuit for generating a comparison voltage having substantially the same value as the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit upon receipt of the supplied drive voltage;
• a comparison circuit which compares the comparison voltage generated by the dummy circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage-supply circuit which generates a voltage in accordance with the level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit and the dummy circuit.

A light emitting apparatus, comprising:

• a differential output circuit which comprises first and second transistors each having a control terminal and first and second terminals, and the first terminals connected to each other and a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second terminal of the second transistor is connected to a power supply voltage source;
• a light emitting element connected between the second terminal of the first transistor and the power supply voltage source;
• an input circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a comparison circuit which compares the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage supply circuit which generates a voltage in accordance with the level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit.

A light emitting apparatus, comprising:

• a differential output circuit which comprises first and second transistors each having a control terminal and first and second terminals, and the first terminals connected to each other and a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second terminal of the second transistor is connected to a power supply voltage source;
• a light emitting element connected between the second terminal of the first transistor and the power supply voltage source,
• an input circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a dummy circuit for generating a comparison voltage having substantially the same value as the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit upon receipt of the supplied drive voltage;
• a comparison circuit which compares the comparison voltage generated by the dummy circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage supply circuit which generates a voltage in accordance with the level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit and the dummy circuit.

A light emitting apparatus comprising:

• a differential output circuit which comprising first and second transistor each having a control terminal and first and second terminals, and can adjust the amounts of current flowing between the first and second terminals in accordance with the level of a signal supplied to the control terminals, and the first terminals connected to each other and which comprises a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second current input/output terminal of the second transistor is connected to a power supply voltage source;
• a light emitting element connected between the second terminal of the first transistor and the power supply voltage source;
• an input circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a comparison circuit which compares the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage supply circuit which generates a voltage in accordance with the input level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit.

A light emitting apparatus, comprising:

• a differential output circuit which comprises first and second transistors each having a control terminal and first and second terminals, and can adjust the amounts of current flowing between the first and second terminals in accordance with the level of a signal supplied to the control terminals, and the first terminals connected to each other and which comprises a current/voltage conversion element connected between a connection point of the first terminals of the first and second transistors and a reference potential, and the second terminal of the second transistor is connected to a power supply voltage source;
• a light emitting element connected between the second terminal of the first transistor and the power supply voltage;
• an input circuit which receives differential drive signals and supplies differential signals in accordance with levels of supplied drive voltages to the control terminals of the first and second transistors of the differential output circuit;
• a reference voltage generation circuit which generates a reference voltage;
• a dummy circuit for generating a comparison voltage having substantially the same value as the potential of the connection point of the first terminals of the first and second transistors of the differential output circuit upon receipt of the supplied drive voltage;
• a comparison circuit which compares the comparison voltage generated by the dummy circuit with the reference voltage and outputs a signal of a level in accordance with the result of comparison;
• and
• a variable voltage supply circuit which generates a voltage in accordance with the level of the output signal of the comparison circuit and supplies the same as the supplied drive voltage to the input circuit and the dummy circuit.