JPH0728073B2 - Semiconductor integrated circuit device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor integrated circuit device that can be used for driving a semiconductor laser device.

2. Description of the Related Art As a drive circuit of a semiconductor laser device, a current switching type drive circuit combining a silicon transistor as a discrete element has been used conventionally.

FIG. 4 is a circuit diagram of a conventional current switching type drive circuit using a silicon transistor. In FIG. 4, Q1 and Q2 are silicon transistors that act as current changeover switches. A semiconductor laser LD is connected between the power supply and the collector of the silicon transistor Q ₁ . φ and silicon transistors Q1 and Q2 respectively
These are non-inverting and inverting inputs that are input to the base of.

The operation of the current switching type drive circuit using the conventional silicon transistor configured as described above will be described below.

The peak current flowing through the semiconductor laser LD is controlled by the base current I _B of the silicon transistor Q3. When the base potential φ of the silicon transistor Q1 is higher than the base potential of the silicon transistor Q2, the silicon transistor Q1 is turned on and current flows to the semiconductor laser LD to emit light.
Conversely, when the base potential φ of the silicon transistor Q1 is lower than the base potential of the silicon transistor Q2, the silicon transistor Q1 is turned off, and no current flows in the semiconductor laser LD, so that the semiconductor laser LD does not emit light.

Problems to be Solved by the Invention However, in the conventional current switching type drive circuit using the silicon transistor, the switching time of the silicon transistors Q1 and Q2 is slow, and therefore the rise and fall times of the peak current flowing through the semiconductor laser are slow. It was Also, because of the combination of discrete elements, the cost of one drive circuit was high.

Therefore, it is conceivable to use a semiconductor material as a compound semiconductor to increase the speed and to integrate circuits to reduce the cost.

However, a compound semiconductor bipolar transistor has not been developed at present, and even if the same circuit configuration as a current switching type drive circuit using a conventional silicon transistor is realized by a compound semiconductor Schottky junction field effect transistor, Since the transition region of the DC transfer characteristic of the circuit is widened due to the characteristics of the transistor, it is difficult to switch the peak current flowing through the semiconductor laser LD.
In order to narrow the transition region and switch the current sufficiently, the circuit configuration becomes complicated and the chip area of the semiconductor integrated circuit device becomes large. Further, since the same circuit configuration as the conventional one requires non-inverting and inverting inputs, the circuit configuration of the input part becomes complicated.

The present invention has been made in view of the above points, and an object thereof is to provide a semiconductor laser driving semiconductor integrated circuit device having a simple circuit configuration.

Means for Solving the Problems In order to solve the above problems, a semiconductor integrated circuit device of the present invention has an input signal conversion circuit for level shifting an input signal, and a waveform shaping of an output signal of the input signal conversion circuit. Of the buffered FET logic circuit and a current drive circuit including a field effect transistor for switching the pulse current according to the output signal of the buffered FET logic circuit and a diode for controlling the peak value of the pulse current.

Effect According to the present invention, a circuit capable of switching a large current required to drive a semiconductor laser at high speed is easily configured.

EXAMPLES Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of a semiconductor integrated circuit device of the present invention. Gallium arsenide (GaAs) is used as the semiconductor material.

As shown in FIG. 1, the semiconductor integrated circuit of the present invention comprises an input signal conversion circuit, a waveform shaping circuit and a current drive circuit. The waveform shaping circuit forms a buffered FEE logic (BFL) circuit. Tr _{1 to} Tr ₇ are all Schottky junction field effect transistors (hereinafter referred to as MESFETs), D _{1 to} D ₇ are all Schottky diodes, R ₁ is a resistor, and input terminal
It has V _IN , output terminal V _OUT , power supply voltage terminals V _DD and V _SS , output peak current control terminal V _IP , and ground terminal GND. The semiconductor laser is connected between the power supply voltage terminal V _DD and the output terminal V _OUT . + 5V and −5 for power supply voltage terminals V _DD and V _SS , respectively
V can be applied. When a TTL level (standard: low level 0.6V, high level 2.2V) signal is input to the input terminal V _IN , it is level-shifted by the Schottky diodes D _{1 to} D ₃ of the input signal conversion circuit, and as a BFL signal of the waveform shaping circuit. Enter the gate of MESFET Tr ₄ . Since the MESFET Tr ₃ and Tr ₄ of the waveform shaping circuit form an inverter circuit, the signal input to the gate of MESFET Tr ₄ is inverted between the high level signal and the low level signal input to the gate of MESFET Tr ₅ . MESFET Tr ₅
The signal that entered the gate of the Schottky diode
D ₄ is level-shifted by to D _6, MESF of the current drive circuit
The voltage level is such that ET Tr ₇ can be switched. With such an input signal conversion circuit, the MESFET Tr ₇ turns on and off.
The switching time is about 1 nS. The current drive circuit consists of MESFET Tr ₇ and Schottky diode D ₇ . When the input is low, the signal entering the gate of the MESFET Tr ₇ is MESFET Tr ₇ is turned ON state at the high level, current flows to the light-emitting semiconductor laser. Conversely, when the input is at high level, the signal entering the gate of MESFET Tr ₇ is at low level, MESFET Tr ₇ is in the OFF state, no current flows to the semiconductor laser, and no light is emitted. The gate potential of MESFET Tr ₇ can also be controlled by the _VIP terminal via Schottky diode D ₇ . The V _IP terminal is an output peak current control terminal, and the peak value of the output current can be controlled by controlling the voltage input to this terminal.

FIG. 2 is a circuit diagram showing a second embodiment of the compound semiconductor integrated circuit of the present invention. Gallium arsenide (GaAs) is used as the semiconductor material.

MESFET Tr _{1 to} Tr ₇ , Schottky diode D _{1 to} D ₇ , resistance
R ₁ , the input terminal V _IN , the power supply voltage terminals V _DD and V _SS , the output peak current control terminal V _IP , and the ground terminal GND are exactly the same as the circuit configuration shown in the first embodiment.

Circuit of this embodiment, MESFET Tr ₈ in parallel with the MESFET Tr ₇ is connected between the output terminal V _OVT ground terminal GND, and also MESFE
It has an output bias current control terminal V _IB for controlling the gate potential of T Tr ₈ . Output bias current control pin V _IB for MESF
By controlling the gate potential of the ET Tr ₈ , a direct current bias current can be passed through the semiconductor laser. ME
Bias current does not flow when the gate potential of SFET Tr ₈ is lower than the threshold voltage of MESFET, and output bias current of about 100mA is obtained when the gate potential is increased (MESFET T
When the gate width of r ₈ is 600 μm). Generally, the relationship between the light emission output L of the semiconductor laser and the current I is as shown in FIG. 3, and light is emitted when the current value is equal to or higher than the threshold current Ith. By controlling the gate potential of the MESFET Tr ₈ by the output bias current control terminal V _IB and supplying a threshold current to the semiconductor laser in advance, the current drive circuit can smoothly drive the semiconductor laser.

EFFECTS OF THE INVENTION As described above, according to the present invention, a semiconductor integrated circuit device for driving a semiconductor laser having a waveform shaping circuit and an output peak current control terminal is realized with an extremely simple circuit configuration and is very useful. .

[Brief description of drawings]

1 and 2 are circuit diagrams of a semiconductor integrated circuit device according to an embodiment of the present invention, FIG. 3 is a characteristic diagram showing the relation between the light emission output of a semiconductor laser and a current, and FIG. 4 is a conventional silicon transistor. FIG. 6 is a circuit diagram of the current switching type drive circuit. Tr _{1 to} Tr ₈ …… MESFET, D _{1 to} D ₇ …… Diode, V _DD , V _SS
...... Power supply voltage terminal, V _IP ...... Output peak current control terminal.

Claims (1)

[Claims] 1. An input signal conversion circuit for level-shifting an input signal, a buffered FET logic circuit for shaping the output signal of the input signal conversion circuit, and a pulse current generated by the output signal of the buffered FET logic circuit. A semiconductor integrated circuit device having a current drive circuit including a field-effect transistor for switching between and a diode for controlling a peak value of a pulse current.