Patent ID: 6510168
Filing Date: 2003-01-21
Classification: H01S,H03K

Abstract:
A laser diode drive circuit comprising:a level shift circuit connected to a drive source, that reduces a drive source voltage by a specific quantity; a current switch that turns on/off a laser diode connected to said drive source; and a switch buffer connected to said level shift circuit, that implements control on said current switch; wherein said level shift circuit varies the quantity by which said drive source voltage is reduced in correspondence to a signal Vset input from the outside; wherein said level shift circuit is provided with a first resistor located between said drive source voltage and said switch buffer and a plurality of resistors connected to said first resistor via a transistor, and a voltage generated at said first resistor is varied by varying a combined resistance of said plurality of resistors; wherein: said plurality of resistors are connected in series; a plurality of switches are provided between said plurality of resistors and the ground; and a decoder that selects one of said plurality of switches in conformance to said signal Vset input from the outside to vary said combined resistance of said plurality of resistors is provided.