Patent ID: 7208931

Claim:
A circuit for generating a constant current, comprising: a reference voltage generating circuit configured to generate a reference voltage; and a constant current circuit including one or more resistors configured to determine an amount of an electric current generated in response to the reference voltage, said one or more resistors being formed of a metal thin film, wherein said reference voltage generating circuit includes: a first power supply circuit configured to produce a first voltage having a positive temperature coefficient, said first power supply circuit including a plurality of field-effect transistors having respective gates, said gates having a common conduction type and different impurity densities, a slope adjusting circuit configured to adjust the positive temperature coefficient of the first voltage produced by said first power supply circuit, said slope adjusting circuit including a field effect transistor and at least one resistor, and a second power supply circuit configured to produce a second voltage having a negative temperature coefficient, to add the second voltage to the first voltage having the temperature coefficient thereof adjusted by said slope adjusting circuit, and thereby to produce the reference voltage having a substantially zero temperature coefficient, said second power supply circuit including a plurality of field-effect transistors having respective gates having different conduction types.