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Abstract

A temperature dependent constant-current generating circuit includes a reference voltage generating circuit for generating a stable reference voltage against the power supply voltage and a temperature change, a stabilized voltage generating circuit for generating a stabilized voltage based on the reference voltage, a voltage divider for dividing the reference voltage, a common-emitter amplifier for amplifying an output voltage from the voltage divider, a current mirror circuit for outputting a current in a direction opposite to an output current from the amplifier, a current-to-voltage conversion resistor connected between the output terminal of the stabilized voltage generating circuit and the output terminal of the current mirror circuit, a buffer amplifier for receiving a voltage generated at the current input terminal of the resistor, and a current feedback output-stage amplifier driven by an output from the buffer amplifier. The constant-current generating circuit can generate a DC bias current which faithfully follows temperature variations in threshold current of an LD and has a high temperature compensation characteristic precision, and is a small-size, low-cost circuit and can be used in an LD driving circuit for fiber-optic subscriber systems including FTTH and optical links.

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First Claim