Laser driving circuit capable of stably controlling laser output
AssigneeKabushiki Kaisha Toshiba
InventorToyoki Taguchi
Life of this patent
Estimating the term…
Abstract
An input signal is supplied to an adder circuit via a gain control amplifier and integrating amplifier and output signals of the gain control amplifier and the integrating circuit are added together by the adder circuit. An output signal of the adder circuit is supplied to a driving current generating circuit. The driving current generating circuit is constituted by first and second transistors whose bases and emitter are commonly connected. An externally attached resistor monitors a driving current flowing in the collector of the transistor constructing the driving current generating circuit and feeds back the current to the gain control amplifier. Therefore, the current control operation of high precision can be attained by use of a part of the driving current.
Claims20
A laser driving circuit comprising:
- a first amplifier for comparing an input signal which controls a light emission intensity of a semiconductor laser with a monitor signal obtained by monitoring a driving current of the semiconductor laser and effecting the control operation to make the input signal and the monitor signal substantially equal to each other;
- a second amplifier connected to an output terminal of said first amplifier;
- an adder circuit for adding together output signals of said first and second amplifiers;
- a driving current generating circuit having an input terminal supplied with an output signal of said adder circuit and an output terminal configured to be connected to the semiconductor laser, for generating a driving current of the semiconductor laser according to the output signal of said adder circuit;
- and
- a terminal to which a resistor for detecting the driving current output from said driving current generating circuit and generating the monitor signal is connected.
A laser driving circuit comprising:
- a first amplifier for comparing an input signal which controls a light emission intensity of a semiconductor laser with a feedback signal obtained by feeding back a driving current of the semiconductor laser and effecting the control operation to make the input signal and the feedback signal substantially equal to each other;
- a second amplifier connected to an output terminal of said first amplifier;
- an adder circuit for adding together output signals of said first and second amplifiers;
- a driving current generating circuit supplied with an output signal of said adder circuit, for generating the driving current of the semiconductor laser, at least part of the driving current being fed back to said first amplifier as the feedback signal;
- and
- a resistor connected to an input terminal of said first amplifier, for detecting the feedback signal fed back from said driving current generating circuit.
A laser driving circuit comprising:
- at least two converting circuits for converting at least two input signals which control a light emission intensity of a semiconductor laser to currents for generating a driving current used for driving the semiconductor laser;
- a current mirror circuit having an input terminal supplied with output signals of said at least two converting circuits;
- a current switch circuit connected to an output terminal of said current mirror circuit, for eliminating a current which is unnecessary for an operation mode of the semiconductor laser from an output signal of said current mirror circuit according to the operation mode of the semiconductor laser to generate a control current;
- and
- a driving current generating circuit having an input terminal supplied with the control current and an output terminal configured to be connected to the semiconductor laser, for generating the driving current of the semiconductor laser according to the control current.
A laser driving circuit comprising:
- at least two converting circuits for converting at least two input signals which control a light emission intensity of a semiconductor laser to currents for generating a driving current used for driving the semiconductor laser;
- a current switch circuit connected to each output terminal of said at least two converting circuits, for eliminating a current which is unnecessary for an operation mode of the semiconductor laser from sum of output signals of said at least two converting circuits according to the operation mode of the semiconductor laser to generate a control current;
- and
- a driving current generating circuit having an input terminal supplied with the control current and an output terminal configured to be connected to the semiconductor laser, for generating the driving current of the semiconductor laser according to the control current.
Dependencies are inferred from the claim text.