Patent ID: 6316990
Filing Date: 2001-11-13
Classification: G05F

Abstract:
A constant current supply circuit for supplying constant current to an electric load, said constant current supply circuit comprising:a primary transistor having a collector connected to one end of said electric load for controlling current supplied to said electric load;a current path resistor, having a resistance temperature coefficient substantially equal to 0, connected between an emitter of said primary transistor and a reference voltage terminal for forming an electric path supplying the current to said electric load via said primary transistor;first, second, third and fourth resistors serially connected in this order between one potential terminal of an electric power source and the other potential terminal of said electric power source;a secondary transistor, being identical in type with said primary transistor, having a collector connected to a connecting point of said second resistor and said third resistor, a base connected to a connecting point of said third resistor and said fourth resistor, and an emitter connected to said other potential terminal of said electric power source; andsaid primary transistor having a base connected to a connecting point of said first resistor and said second resistor.