Laser diode driver

Abstract

There is provided a current switching circuit that adds additional current in accordance with an intensity of output current to input current of a current mirror at a rising edge of the output current of the current mirror. The current switching circuit includes a MOS transistor outputting the additional current upon receiving ON potential at a gate terminal, and a slope of a leading edge waveform of a pulse signal providing the ON potential is controlled in accordance with the intensity of the output current.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a circuit diagram showing a first embodiment of the present invention;

FIG. 2 is a view showing the waveforms of the elements in FIG. 1;

FIG. 3 is a circuit diagram showing another example of the first embodiment of the present invention;

FIG. 4 is a circuit diagram showing a second embodiment of the present invention;

FIG. 5 is a circuit diagram showing another example of the second embodiment of the present invention; and

FIG. 6 is a circuit diagram showing a related art.

Claims

1. A current switching circuit that adds additional current in accordance with an intensity of output current to input current of a current mirror at a rising edge of the output current of the current mirror, comprising: a MOS transistor outputting the additional current upon receiving ON potential at a gate terminal, a slope of a leading edge waveform of a pulse signal providing the ON potential being controlled in accordance with the intensity of the output current.

2. The current switching circuit according to claim 1, further comprising: a variable resistor controlling the slope of the leading edge waveform.

3. The current switching circuit according to claim 2, wherein the variable resistor comprises a second current mirror receiving current in accordance with the intensity of the output current and outputting the ON potential at the rising edge of the output current.

4. The current switching circuit according to claim 3, wherein the second current mirror comprises a constant current source supplying idling current.

5. A current switching circuit comprising: a first current mirror outputting second current proportional to input first current;a variable current source generating the first current;a current energized circuit generating third current to be added to the first current at the rising edge of the second current, in accordance with an intensity of the second current, the current energized circuit including:a MOS transistor outputting the third current; anda controller controlling a slope of a leading edge waveform of a pulse signal providing ON potential to be supplied to a gate terminal of the MOS transistor, in accordance with the intensity of the second current at the rising edge of the second current.

6. The current switching circuit according to claim 5, wherein the controller is a variable resistor connected between a power supply of the ON potential and the gate terminal of the MOS transistor.

7. The current switching circuit according to claim 6, wherein the variable resister comprises a second current mirror receiving current in accordance with the intensity of the second current and outputting the ON potential at a rising edge of the second current.

8. The current switching circuit according to claim 7, wherein the second current mirror comprises a constant current source supplying idling current.

9. The current switching circuit according to claim 5, further comprising: a switch controlling the rising edge of the second current by a first control signal, disposed on an input side of the first current mirror.

10. The current switching circuit according to claim 5, further comprising: a switch controlling the rising edge of the second current by a first control signal, disposed between an input side and an output side of the first current mirror.

11. The current switching circuit according to claim 9, further comprising: a one-shot circuit generating a second control signal to activate supply of the ON potential to the MOS transistor in synchronization with a leading edge of the first control signal.

12. A current switching circuit comprising: a first current mirror outputting second current proportional to input first current;a variable current source generating the first current;a MOS transistor outputting third current to be added to the first current at the rising edge of the second current, in accordance with an intensity of the second current, the third current; anda controller controlling a slope of a leading edge waveform of a pulse signal providing ON potential to be supplied to a gate terminal of the MOS transistor in accordance with the intensity of the second current at the rising edge of the second current.