JPS62296572A - Semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To constitute a circuit capable of switching large currents at high speed simply by organizing the circuit of an input signal conversion circuit, a waveform shaping circuit and a current drive circuit. CONSTITUTION:When a signal at a TTL level is transmitted over an input terminal VIN, the signal is level-shifted by Schottky diodes D1-D3 for an input signal conversion circuit, and enters an MESFET Tr4 for a waveform shaping circuit as a BFL signal. Since MESFETs Tr3 and Tr4 for the waveform shaping circuit construct an inverter circuit, a signal where a high level and a low level are inverted to a signal transmitted over the gate for the MESFET Tr4 enters a gate for an MESFET Tr5. The signal transmitted over the gate for the MESFET Tr5 is level-shifted by Schottky diodes D4-D6, and brought to a voltage level capable of switching an MESFET Tr7 for a current drive circuit. The switching times of ON-OFF of an MESFET Tr8 are all brought to approxi mately 1nS by such an input signal conversion circuit.

Description

3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a semiconductor integrated circuit device that can be used to drive a semiconductor laser device.

2. Description of the Related Art As a drive circuit for a semiconductor laser device, a current switching type drive circuit in which two silicon transistors as discrete elements are combined has been used.

FIG. 4 shows a circuit diagram of a current switching type drive circuit using conventional silicon transistors. In FIG. 4, Ql and Q2 are silicon transistors that function as current changeover switches. A semiconductor laser LD is connected between the power supply and the collector of the silicon transistor Q2. φ, <6 are non-inverting and two inverting inputs input to the bases of silicon transistors Q1 and Q2, respectively.

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

The peak current flowing through the semiconductor laser LD is controlled by the base current IB of the silicon transistor Q3. When the base potential φ of the silicon transistor Q1 is higher than the base potential (1) of the silicon transistor Q2, the silicon transistor Q1 is turned on, and a current flows through the semiconductor laser LD to emit light.

Conversely, when the base potential φ of the silicon transistor Q1 is lower than the base potential j of the silicon transistor Q2, the silicon transistor Q1 is turned off, and no current flows to the semiconductor laser LD and no light is emitted.

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

Therefore, it is possible to increase the speed by using compound semiconductors as the semiconductor material, and to reduce costs by integrating the circuits.

However, compound semiconductor bipolar transistors have not yet been developed, and even if the same circuit configuration as a current switching type drive circuit using conventional silicon transistors is realized using compound semiconductor Schottky junction field effect transistors, the Schottky junction field effect Due to the characteristics of the transistor,
Since the transition region of the DC transfer characteristic of the circuit becomes wide, 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 increases. Furthermore, the same circuit configuration as the conventional one requires nine non-inverting and inverting inputs, which makes the circuit configuration of the input portion complicated.

The present invention has been made in view of this point, and an object of the present invention is to provide a semiconductor integrated circuit device for driving a semiconductor laser with a simple circuit configuration.

Means for Solving the Problems In order to solve the above problems, the semiconductor integrated circuit device of the present invention includes an input signal conversion circuit for level shifting an input signal, and a device for waveform shaping the output signal of the input signal conversion circuit. The buffer art FET logic circuit has a current drive circuit consisting of a field effect transistor that switches the pulse current according to the output signal of the buffer art FET logic circuit, and a diode that controls the peak value of the pulse current.

Effects According to the present invention, a circuit capable of rapidly switching a large current required to drive a semiconductor laser can be easily constructed.

EXAMPLES Hereinafter, examples of the present invention will be described 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 includes an input signal conversion circuit, a waveform shaping circuit, and a current drive circuit. The waveform shaping circuit forms a BFL circuit. "r1~
Tr7 are all Schottky junction field effect transistors (hereinafter referred to as MESFETs), D1 to D7 are all Schottky diodes, R1 is a resistor, input terminal V is connected to N, and output terminal V. UT, power supply voltage terminals vDD and vs
s, an output peak current control terminal VIP, and a ground terminal GND. The semiconductor 6 to 12' laser is connected between the power supply voltage terminal vDD and the output terminal voUT. +5V and -5V are applied to power supply voltage terminals vDD and vss, respectively.

Input terminal v! N to TTL level (standard *: Laurepel o
, eV, high level 2, 2V), it is level-shifted by the Schottky diodes D1 to D3 of the input signal conversion circuit, and is sent as a BFL signal to the ME of the waveform shaping circuit.
Enter the gate of SFET T, 4. M of waveform shaping circuit
Since the ESFETs Tr3 and "r4 constitute an inverter circuit, the gate of the MESFET Tr6 receives a signal having a high level and a low level that are inverted from the signal that entered the gate of the MESFET"r4. MES
The signal input to the gate of FET Tr5 is further level-shifted by Schottky diodes D4 to D6, and becomes a voltage level that can switch MESFET Tr□ of the current drive circuit. MESFET Tr8 is turned on by such an input signal conversion circuit.

The OFF switching time is about Ins in both cases. The current drive circuit consists of MESFETs T, 777... and Schottky diode D7. When the input is at low level, the signal entering the gate of MESFET Tr7 is at high level and MESFET Tr□ is turned on, causing current to flow through the semiconductor laser and emitting light. Conversely, when the input is high level, the signal entering the gate of MESFET Tr□ is low level, and MESFET Tr□ is OF
It enters the F state, and no current flows through the semiconductor laser and it does not emit light. The gate potential of MESFET Tr7 can also be controlled by the V input P terminal via the Schottky diode D7. ■The P terminal is an output peak current control terminal, and by controlling this terminal, the peak value of the output current can be controlled.

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 Tx1~Tr□, Schottky diode D1~D7, resistor R1, input terminal ■■N, power supply voltage terminal vDD and vss, output peak current control terminal ■1P1
Regarding the ground terminal GND, the circuit configuration is exactly the same as that shown in the first embodiment.

The circuit of this example has M
ESFET Tr8 connects output terminal vovT and ground terminal G
It is connected between NDO and has an output bias current control terminal (2) for controlling the gate potential of MESFET Tr8. MES at output bias current control terminal v1B
By controlling the gate potential of FET Tr8, a direct current bias current can be passed through the semiconductor laser. The gate potential of MESFET Tr8 is
If the voltage is below the threshold voltage of T, the bias current will not flow,
As the gate potential is increased, an output bias current of about 100 mA is obtained (when the gate width of MESFET Tr8 is 600 μm). Generally, the relationship between the light emitting output of a 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.

The output bias current control terminal vIB allows the MESFE
By controlling the gate potential of the TTr 8 and causing a threshold current to flow through the semiconductor laser in advance, the semiconductor laser can be smoothly driven by the current drive circuit 91.

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 explanation of the drawing]

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 relationship between the light emitting output and current of a semiconductor laser, and FIG. 4 is a diagram using a conventional silicon transistor. FIG. 3 is a circuit diagram of a current switching type drive circuit according to the present invention. T-T...FET1D1~D7...
...Diode r1 r7 -de, vDD, vss ...4...Power supply voltage terminal,
vIP...Output peak control terminal. Name of agent: Patent attorney Toshio Nakao and one other person
1~Ding〒ri1--FET D/~D7- Diode Vvo Vss--One electric 1fffi! Child VIP---
Output Pig control snoring Fig. 1 Fig. 2 JP-A-1'18G2-296572 (4) Fig. 3 ψ, φ - Person force Q 7. Q2 - Rough cut layer Sj) Transistor Q3 - Constant current - 3 SL transistor LD - One semiconductor main ν - The upper LD in Fig. 4 φ Qf Q2 ψ

Claims (1)

[Claims] an input signal conversion circuit for level shifting an input signal; a buffered FET logic circuit for waveform shaping an output signal of the input signal conversion circuit; and the buffered FET.
1. A semiconductor integrated circuit device comprising a current drive circuit comprising a field effect transistor that switches a pulse current according to an output signal of a logic circuit and a diode having a control terminal that controls the peak value of the pulse current.