JPH077204A - Semiconductor laser device drive circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] In a driver circuit using GaAs MESFETs, a constant output current amplitude is obtained even if the power supply voltage fluctuates. [Structure] In a GaAs MESFET driver circuit, a potential detection circuit 13 is provided on the drain side of the output FET 4 to obtain an average value of the output current amplitude, and this and the reference current source 1
The output of No. 2 is compared and amplified by the differential amplifier 14, and the output is input to the voltage controlled current source 15. The voltage controlled current source 15 has an output current I1 proportional to the input voltage. This is used as the reference current of the current mirror current source and controlled to obtain a constant I2, that is, the output current amplitude. [Effect] The reference current of the current mirror current source is controlled only by adding a simple DC circuit so that a stable output current amplitude can be obtained even when the power supply voltage changes, and a constant output current amplitude can be obtained constantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, GaAsME.
In a semiconductor laser device driving circuit using SFET,
The present invention relates to a semiconductor laser element drive circuit that can obtain a stable output amplitude without changing the output current amplitude even if the power supply voltage changes.

[0002]

2. Description of the Related Art Conventional Example 1. FIG. 6 shows, for example, JP-A-3-21.
Conventional GaAs MESFET disclosed in Japanese Patent No. 4935
This is a partial modification of the driver, and the current source is a current mirror type current source. In the figure, 1 is a positive phase data input terminal, 2 is a negative phase data input terminal, 3 and 4 are FETs of a differential pair, 5 is a laser diode LD, 6 is a load resistor, and 7 and 8 are current mirror type current sources. FE to configure
T, 9 and 10 are emitter resistors, and 11 is a diode for temperature compensation. FIG. 7 shows GaAs MESF for explanation.
It is the figure which showed the static characteristic of ET.

The operation of the conventional GaAs MESFET driver circuit will be described below. Positive phase data input terminal 1
When the positive phase data and the negative phase data are input to the negative phase data input terminal 2, the FETs 3 and 4 in the differential pair configuration perform a switching operation, the FET 3 corresponds to the normal phase data, and the FET 4 corresponds to the reverse phase data. The current is extended to the LD and the load resistor 6.
FETs 7 and 8 form a current mirror circuit F
ET and has emitter resistors 9 and 10. If the resistance values of the emitter resistors 9 and 10 are equal, F
A current almost equal to I1 flowing through ET7 is FE as I2.
It flows to T8, and this I2 determines the PP value of the output current waveform of the FETs 3 and 4. This principle will be described below.

First, the current I1 determined by the FET 7, its emitter resistance 9 and the temperature compensating diode 11 is expressed by the following equation. I1 = (V _CC −V _GS1 −V _F ) / R where V _GS1 is the gate-source voltage of the FET 7, V
_F is a voltage drop generated in the temperature compensating diode 11, R
Is the resistance value of the resistor 9. On the other hand, the gate of FET8 is F
Since it is connected to the gate of ET7, it has the same potential. F
Assuming that the ETs 7 and 8 have the static characteristics shown in FIG. 7, the current I2 that flows regardless of the V _DS of the FET 8 becomes equal to I1, and the output waveform having this I2 as the PP value is FE.
It will be obtained at T3 and 4.

Conventional example 2. FIG. 8 shows, for example, JP-A-4-245.
This is a conventional semiconductor laser device driving circuit disclosed in Japanese Patent No. 691. In the figure, 31 is a laser diode, 32 is a photodiode, 33 is a buffer circuit, 34, 35 and 36 are reference current sources, 37, 38 and 39 are amplifiers, 4
0 is a peak hold circuit, 41 is a bottom hold circuit,
42 and 43 are differential amplifiers.

The operation of the conventional semiconductor laser device driving circuit will be described below. In the semiconductor laser device driving circuit of FIG. 8, the output light of the laser diode 31 is monitored by the photodiode 32, and the current supplied to the laser diode 31 is changed so that the maximum value and the minimum value of the emission output of the laser diode 31 are always constant. It is configured to let. That is, the input signal DATA and the inverted input signal DATA are applied to the bases of the transistors Q1 and Q2 via the buffer circuit 33, respectively. The laser diode 31 has a power supply Vc
It is inserted between c and the collector of the transistor Q1.

The collector of the transistor Q1 is further connected to the collector of the transistor Q4 via the solenoid 44, and the collector of the transistor Q2 is connected to the power supply Vcc. The emitters of the transistors Q1 and Q2 are commonly connected to the collector of the transistor Q3, and the emitter of the transistor Q3 is grounded via the resistor R1.

The output of the differential amplifier 42 is applied to the base of the transistor Q3. The differential amplifier 42 receives the output of the peak hold circuit 40 and the output of the amplifier 38 for converting the reference current I2 into a voltage. The amplifier 37 compares and amplifies the output of the photodiode 32 and the reference current I1, converts the voltage, and outputs the voltage to the peak hold circuit 40. On the other hand, the output of the differential amplifier 43 is applied to the base of the transistor Q4. The differential amplifier 43 receives the output of the bottom hold circuit 41 and the output of the amplifier 39 that converts the reference current I3 into a voltage. The amplifier 37 compares and amplifies the output of the photodiode 32 and the reference current I1, converts the voltage, and outputs the voltage to the bottom hold circuit 41. The emitter of the transistor Q4 is grounded via the resistor R2. One end of the photodiode 32 is connected to the power supply Vcc.

In the semiconductor laser device driving circuit, the modulation current flowing through the laser diode 31 by the output of the differential amplifier 42 which receives the difference between the maximum output current of the photodiode 32 and the reference current I1 and the reference current I2. The value of is determined. Further, the value of the bias current flowing through the laser diode 31 is determined by the output of the differential amplifier 43 which inputs the minimum value of the output current to the photodiode 32, the difference current between the reference current I1 and the reference current I3. Therefore, regarding the light emission output of the laser diode 31, the maximum light output is determined by the reference currents I1 and I2, the minimum light output is determined by the reference currents I1 and I3, and the average light output and the extinction ratio are determined by the reference currents I1 to I3. To be done.

[0010]

As shown in THE INVENTION Problems to be Solved] Conventional Example 1, I the variation of V _DS is also static characteristics GaAsMESFET in the driver circuit using a GaAsMESFET characteristics shown in FIG. 9, i.e. in the saturation region of the transistor _D If V _DS fluctuates due to power fluctuation, I2 fluctuates even though I1 of the current mirror current source is constant, which causes P-P of the output waveform of the differential pair FET. There was a problem that the value fluctuated.

Further, in the semiconductor laser device driving circuit shown in the second conventional example, the peak hold circuit and the bottom hold circuit are circuits that require high speed operation, and are composed of higher speed devices as the transmission bit rate increases. Need to be done. A transmission bit rate of 2 Gb / s or more is assumed when a semiconductor laser element drive circuit is configured using GaAs MESFETs, but it is difficult to manufacture the peak hold circuit and the bottom hold circuit with high yield in such high-speed optical transmission. become.

When a semiconductor laser device driving circuit using GaAs MESFET is used to construct a high bit rate optical transmitter, the ATC is performed in order to stabilize the characteristics of the laser device.
(Automatic Temperature Control) circuit is used. This is a circuit that keeps the junction temperature of the laser diode constant and the PI characteristic of the laser diode constant. If the temperature characteristic of the laser diode is constant, the amplitude of the optical output and the extinction ratio can be kept constant if the modulation current amplitude of the semiconductor laser element drive circuit is always constant.

However, the semiconductor laser device driving circuit using the GaAs MESFET is very sensitive to the fluctuation of the power supply voltage, and the fluctuation of the power supply voltage causes the fluctuation of the output amplitude. The cause will be described below with reference to FIGS. 9 and 10.

FIG. 10 shows a simplified semiconductor laser device drive circuit using GaAs MESFETs. In the figure, the positive phase signal DATA and the negative phase signal DATA are input to the gates of the FETs Q1 and Q2, the laser LD and the load resistor R1 are provided between the drains of Q1 and Q2 and Vcc, and the positive phase signal DATA and the negative phase signal DATA are supplied. It is configured so that a compliant current flows. The sources of the FETs Q1 and Q2 are commonly connected to the drain of the FET Q3,
The source of is grounded. A reference current source I1 is connected to the gate of the FET Q3 to form a current mirror type current source, and a current I2 almost equal to I1 is made to flow as a drain current. In this semiconductor laser device drive circuit, the static characteristics of the GaAs MESFET are those shown in FIG. 9, that is, V in the saturation region of the transistor.
Consider a case where I _D has a characteristic that it fluctuates depending on the fluctuation of _DS . The positive phase signal DATA and the negative phase signal DATA are generally Vc.
regulated to the c side, that is, FETs Q1 and Q2
The gate of is also fixed when viewed from Vcc. If the power supply fluctuation causes Vcc to change from the initial value Vcc1 to Vcc2 by Δ
It is assumed that it fluctuates with Vcc. At this time, the V _DS of the FET Q3 is changed from the initial value V _DS (@ Vcc1) to V _DS (@ Vcc2) by ΔV.
It varies by cc. At this time, the output current I2 of the FET Q3 changes by ΔI _D. FETQ1 and for equal output current I2 of the output current amplitude Q3 of Q2, that is, the output current amplitude is also a problem that only fluctuates [Delta] I _D.

The present invention has been made to solve the above problems, and in a semiconductor laser device driving circuit using a device such as GaAs MESFET, Ga
It is an object of the present invention to realize a circuit that can obtain a stable output current amplitude even if the power supply voltage fluctuates regardless of the static characteristics of an element such as AsMESFET by adding a simple DC circuit.

[0016]

A semiconductor laser device driving circuit according to claim 1 is provided with a reference voltage source, a potential detection circuit, a differential amplifier and a voltage control current source, and the output current amplitude is used as an average value in the potential detector. The output voltage of the current mirror circuit is detected even when the power supply voltage fluctuates. It is provided with a means for controlling the current I1.

A semiconductor laser device driving circuit according to a second aspect is provided with a mark ratio detecting circuit, a potential detecting circuit, a differential amplifier and a voltage control current source, and the P-P value of the output current waveform is used as an average value in the potential detecting circuit. The output voltage of both is compared with the mark ratio detection circuit as a reference instead of the reference voltage source, amplified by the differential amplifier circuit, and then output by the voltage controlled current source controlled by the output voltage. However, a means for controlling the reference current I1 of the current mirror circuit is provided even when the mark ratio changes in addition to the power supply voltage change.

According to another aspect of the semiconductor laser device driving circuit of the present invention, a reference voltage source, a power supply voltage detection circuit, a differential amplifier and a voltage controlled current source are provided, and both outputs of the power supply voltage detection circuit and the reference voltage source are supplied to the differential amplifier. It is configured to be output by a voltage controlled current source controlled by the output voltage after being amplified by the output voltage, and means for controlling the reference current I1 of the current mirror circuit even when the power supply voltage fluctuates. .

[0019]

The semiconductor laser device driving circuit according to the present invention is configured so that the reference current I1 of the current mirror circuit is controlled so that I2 and the output current amplitude are constantly constant.

The principle of stabilizing the output current amplitude according to the present invention will be described with reference to FIG. FIG. 1 shows an example of static characteristics of a GaAs MESFET. Initially GaAsME
Assuming that the SFET has V _GS1 and V _DS1 , the drain current generated at this time is I _D1 . If V _DS1 becomes V _DS2 due to the decrease in power supply voltage, the drain current also decreases and becomes I _D2 (arrow A). At this time V _GS
Is controlled to V _GS2 , I _D2 becomes the original I _D1 (arrow B). When the power supply voltage is increased, the drain current remains I _D1 (arrow C,
D). According to the present invention, V _GS is equivalently controlled by controlling the current.

[0021]

EXAMPLES Example 1. FIG. 2 is a diagram showing an embodiment of a semiconductor laser device driving circuit according to the invention described in claim 1.
In the figure, 1 is a positive phase data input terminal, 2 is a negative phase data input terminal, 3 and 4 are differential pair FETs, 5 are LDs, 6 are load resistors, and 7 and 8 are current mirror type current sources. FETs, 9 and 10 are source resistors, 12 is a reference voltage source, 13 is a potential detection circuit, 14 is a differential amplifier, and 15 is a voltage controlled current source. The potential detection circuit 13 is connected to the drain of the FET 4 and detects a voltage drop caused by the load resistance 6. The outputs of the reference voltage source 12 and the potential detection circuit 13 are input to the differential amplifier 14, and the output of the differential amplifier 14 is connected to the voltage controlled current source 15. The output of the voltage controlled current source 15 is connected to the drain of the FET 7.

Next, the operation will be described. When a data signal is input to the positive phase data input terminal 1 and the negative phase data input terminal 2, the FETs 3 and 4 in the differential pair configuration perform a switching operation, the FET 3 corresponds to the normal phase data, and the FET 4 corresponds to the negative phase data. Is output to the LD 5 and the load resistor 6. F
ETs 7 and 8 are FEs forming a current mirror circuit
T and has source resistors 9 and 10. If the source resistors 9 and 10 have the same resistance value, a current substantially equal to the current I1 flowing in the FET 7 flows as I2 in the FET 8, and the output current amplitude value of the FETs 3 and 4 is determined by this I2. Here, the reference voltage source 12 has a constant output voltage regardless of the power supply voltage. The potential detection circuit 13 is FE
It is connected to the drain of T4 and detects the voltage drop due to the load resistance 6. The potential detection circuit 13 has a band lower than the transmission speed and averages the output current amplitude value of the FET 4 (averages the P-P value of the output current waveform) and outputs it as a DC voltage. The differential amplifier 14 compares and amplifies the two output voltages and inputs the output to the voltage controlled current source 15. The voltage controlled current source 15 is configured to have an output current proportional to the input voltage, and its output is input to the FET 7 and becomes the reference current I1 of the current mirror circuit.

Now, due to the decrease of the power supply voltage, V _DS of the FET 8
Is decreased, and the output current amplitude value (P-P value of the output current waveform) of the differential pair FETs 3 and 4 is decreased. At this time, the input of the potential detection circuit 13 rises (approaches Vcc), and the output also rises accordingly. On the other hand, the output of the reference voltage source 12 is fixed. The differential amplifier 14 receives this and the potential detection circuit 1
The output fluctuation of 3 is multiplied by G and then output. Voltage controlled current source 15
In response to this, the output current I1 increases. This result I1
When I increases, I2 also increases and the output current amplitude value (P-P value of the output current waveform) of the differential pair FETs 3 and 4 increases to the original value. When the power supply voltage increases, the reverse operation occurs and the output current amplitude value (PP of the output current waveform
Value) is the original value.

In FIG. 2, the potential detection circuit 13 is connected to the drain terminal of the FET 4 on the opposite phase side of the pair of differential FETs 3 and 4, but as shown in FIG. 13 is a pair of differential FETs 3 and 4
Of these, it may be connected to the drain terminal of the positive-phase side FET 3.

As described above, in this embodiment, the positive-phase data input terminal, the negative-phase data input terminal, and the pair of Ga having a differential structure are used.
AsMESFET, a load connected to the drains of the pair of FETs, a FET as a current source whose drain is connected to the common source of the pair of FETs, and a reference as a current mirror circuit configuration with the FET as the current source In a GaAs MESFET semiconductor laser device driving circuit including a current source, a reference voltage source, a potential detection circuit connected to the drain terminals on the positive phase side or the negative phase side of a pair of FETs of the differential configuration, and the reference voltage source. And a potential detection circuit for comparing and amplifying both outputs, and a voltage controlled current source having the output of the differential amplifier as an input, the output of which is connected to the input of the reference current source of the current mirror configuration. It is characterized by

Example 2. FIG. 4 is a block diagram showing an embodiment of the invention described in claim 2. In the figure, 1 to 10 are the same as in the first embodiment. Reference numeral 13 is a potential detection circuit, 14 is a differential amplifier, 15 is a voltage controlled current source, and 16 is a mark ratio detection circuit. The mark ratio detection circuit 16 has a positive phase data input terminal 1
(Or negative-phase data input terminal 3), and its output is connected to the differential amplifier 14.

Next, the operation will be described. GaAsME
The operations of the SFET semiconductor laser device driving units 1 to 10 are the same as in the first embodiment. The mark ratio detection circuit 16 detects the mark ratio from the positive or negative phase data and outputs it. The output is input to the differential amplifier 14 and becomes the reference voltage. Potential detection circuit 1
3 is connected to the drain of the FET 4 and detects a voltage drop due to the load resistor 6. The potential detection circuit 13 has a band lower than the transmission speed, and the output current waveform of the FET 4 is P-.
The P value is averaged and output as a DC voltage. Differential amplifier 1
At 4, the two output voltages are compared and amplified, and the output is input to the voltage controlled current source 15. The voltage controlled current source 15 is configured to have an output current proportional to the input voltage, and its output is input to the FET 7 and becomes the reference current I1 of the current mirror circuit. Now, due to the decrease of power supply voltage, V of FET8
_DS decreases, P- of the output current waveform of the differential pair FETs 3 and 4
It is assumed that the P value has decreased. At this time, the input of the potential detection circuit 13 rises (approaches Vcc), and the output also rises. On the other hand, the output of the mark ratio detection circuit 16 is fixed at each mark ratio. 14 receives this and the potential detection circuit 13
The output fluctuation of is multiplied by G and then output. The voltage controlled current source 15 receives this and the output current I1 increases. As a result, if I1 increases, I2 also increases, and the P-P value of the output current waveform of the differential pair FETs 3 and 4 increases to the original value. When the power supply voltage increases, the opposite operation occurs and the P-P value of the output current waveform becomes the original value. When the mark rate changes, the mark rate detection circuit 16 and the potential detection circuit 1
Since the output of 3 also changes in proportion to it, a stable output current amplitude value (PP value of the output current waveform) can be obtained even when the mark ratio changes.

As described above, this embodiment has a positive phase data input terminal, a negative phase data input terminal, and a differential pair of GaAsMs.
ESFET, a load connected to the drains of the pair of FETs, a FET serving as a current source whose drain is connected to a common source of the pair of FETs, and a reference serving as a current mirror circuit configuration with the FET serving as the current source In a GaAs MESFET semiconductor laser device drive circuit including a current source, a mark ratio detection circuit connected to the positive phase data input terminal or the negative phase data input terminal to detect the mark ratio, and a pair of differential FETs. A potential detection circuit connected to the drain terminal on the positive phase side or the negative phase side, a differential amplifier for comparing and amplifying both outputs of the mark ratio detection circuit and the potential detection circuit, and an input of the differential amplifier output, The output comprises a voltage controlled current source connected to the input of the reference current source of the current mirror configuration.

Example 3. FIG. 5 is a diagram showing an embodiment of the invention described in claim 3. In the drawings, 1 to 10 are the first embodiment
Is the same as. Reference numeral 12 is a reference voltage source, 17 is a power supply voltage detection circuit, 14 is a differential amplifier circuit, and 15 is a voltage controlled current source. The output of the reference voltage source 12 and the output of the power supply voltage detection circuit 17 are input to the differential amplifier circuit 14, and the differential amplifier circuit 14
Is connected to the voltage controlled current source 15. The output of the voltage controlled current source 15 is connected to the drain of the FET 7.

Next, the operation will be described. GaAsME
The operation of the SFET semiconductor laser device drivers 1 to 10 is the same as that of the first embodiment. The reference voltage source 12 has a constant output voltage regardless of the power supply voltage. The power supply voltage detection circuit 17 outputs a voltage proportional to the power supply voltage. The differential amplifier 14 compares and amplifies the two output voltages and inputs the output to the voltage controlled current source 15. The voltage controlled current source 15 is configured to have an output current proportional to the input voltage, and its output is input to the FET 7 and becomes the reference current I1 of the current mirror circuit. Now, when the power supply voltage decreases, the output of the power supply voltage detection circuit 17 decreases (approaches to GND), and thus the output also decreases. On the other hand, the output of the reference voltage source 12 is fixed. The differential amplifier 14 receives this and multiplies the output fluctuation of the power supply voltage detection circuit 17 by G and outputs it. At this time, G is the output current amplitude value (PP of the output current waveform
It is necessary to set so that the value) is constant. At 15, the output current I1 increases accordingly. As a result, if I1 increases, I2 also increases and the output current amplitude value (P-P value of the output current waveform) of the differential pair FETs 3 and 4 increases to the original value. When the power supply voltage increases, a reverse operation occurs, and the output current amplitude value (PP value of the output current waveform) becomes the original value.

As described above, in this embodiment, the positive-phase data input terminal, the negative-phase data input terminal, and the pair of Ga having a differential structure are used.
AsMESFET, a load connected to the drains of the pair of FETs, a FET as a current source whose drain is connected to the common source of the pair of FETs, and a reference as a current mirror circuit configuration with the FET as the current source In a GaAs MESFET semiconductor laser device drive circuit including a current source, a reference voltage source, a power supply voltage source detection circuit, a differential amplifier for comparing and amplifying both outputs of the reference voltage source and the power supply voltage detection circuit, and the differential circuit. An amplifier output is used as an input, and the output is provided with a voltage controlled current source connected to the input of the reference current source of the current mirror configuration.

[0032]

As described above, according to the first and third aspects of the invention, in the semiconductor laser device driving circuit, a simple D
A semiconductor laser element drive circuit having a stable output current amplitude even when the power supply voltage changes can be obtained only by adding the C circuit. According to the second aspect of the present invention, the output current amplitude can be kept constant even when the power supply voltage changes and the mark ratio changes.

[Brief description of drawings]

FIG. 1 is a principle diagram of a method of compensating for static characteristics of a GaAs MESFET according to the present invention.

FIG. 2 is a diagram showing an embodiment of the invention according to claim 1;

FIG. 3 is a diagram showing an embodiment of the invention according to claim 1;

FIG. 4 is a diagram showing an embodiment of the invention according to claim 2;

FIG. 5 is a diagram showing an embodiment of the invention according to claim 3;

FIG. 6 is a diagram showing a conventional semiconductor laser device driving circuit.

FIG. 7 is a static characteristic diagram of GaAs MESFET.

FIG. 8 is a diagram showing a conventional semiconductor laser device driving circuit.

FIG. 9 is a static characteristic diagram of GaAs MESFET.

FIG. 10 is a schematic diagram of a GaAs MESFET semiconductor laser device driving circuit.

[Explanation of symbols]

 1 Positive phase data input terminal 2 Reverse phase data input terminal 3 GaAsMESFET 4 GaAsMESFET 5 Light source LD 6 Load resistance 7 GaAsMESFET 8 GaAsMESFET 9 Emitter resistance 10 Emitter resistance 11 Temperature compensation diode 12 Reference voltage source 13 Potential detection circuit 14 Differential Amplifier 15 Voltage controlled current source 16 Mark ratio detection circuit 17 Power supply voltage detection circuit 31 Laser diode 32 Photodiode 33 Buffer circuit 34 Reference current source 35 Reference current source 36 Reference current source 37 Amplifier 38 Amplifier 39 Amplifier 40 Peak hold circuit 41 Bottom hold Circuit 42 differential amplifier 43 differential amplifier

Claims (3)

[Claims] 1. A positive-phase data input terminal, a negative-phase data input terminal, a pair of differential FETs, a load connected to the drains of the pair of FETs, and a drain connected to a common source of the pair of FETs. FET as a connected current source
And a semiconductor laser device driving circuit including an FET as the current source and a reference current source having a current mirror circuit configuration, and a reference voltage source and a pair of FEs having the differential configuration.
A potential detection circuit connected to the drain terminal on either the positive phase side or the negative phase side of T, a differential amplifier for comparing and amplifying both outputs of the reference voltage source and the potential detection circuit, and the differential amplifier output are input. A semiconductor laser device drive circuit, the output of which is provided with a voltage controlled current source connected to the input of the reference current source of the current mirror circuit configuration. 2. A positive phase data input terminal, a negative phase data input terminal, a pair of differential FETs, a load connected to the drains of the pair of FETs, and a drain connected to a common source of the pair of FETs. FET as a connected current source
And a semiconductor laser device drive circuit including an FET as the current source and a reference current source having a current mirror circuit configuration, which is connected to the positive phase data input terminal or the negative phase data input terminal to detect the mark ratio. A mark ratio detection circuit, a potential detection circuit connected to a drain terminal on either the positive phase side or the negative phase side of the pair of differential FETs, and both outputs of the mark ratio detection circuit and the potential detection circuit. A semiconductor laser device comprising: a differential amplifier for comparative amplification; and a voltage-controlled current source that receives the output of the differential amplifier and that output is connected to the input of a reference current source of the current mirror circuit configuration. Drive circuit. 3. A positive-phase data input terminal, a negative-phase data input terminal, a pair of differential FETs, a load connected to the drains of the pair of FETs, a power supply connected to the load, and FET as a current source whose drain is connected to a common source of a pair of FETs, and F as the current source
In a semiconductor laser device driving circuit including ET and a reference current source having a current mirror circuit configuration, a reference voltage source, a power supply voltage detection circuit, and a difference for comparing and amplifying both outputs of the reference voltage source and the power supply voltage detection circuit. A semiconductor laser device driving circuit comprising: a dynamic amplifier; and a voltage controlled current source having an output of the differential amplifier as an input and having an output connected to an input of a reference current source having the current mirror circuit configuration.