JPS61131610A - Semiconductor circuit - Google Patents

Abstract

PURPOSE:To improve the linearity of the period and to reduce the period by applying a constant current to a capacitor in parallel with a semiconductor element of an S-shaped negative resistive characteristic and suppressing a voltage across the capacitor when said element is turned on. CONSTITUTION:A constant current I is fed to the capacitor C during a period t1 with a diode D turned off and the terminal voltage Vc rises linearly from a small value Vf. A transistor (TR) acts like flowing the constant current I to a resistor R1. When the terminal voltage Vc of the capacitor C reaches a transfer point Vt of the diode D, the diode D is turned on, the capacitor C starts discharging, an attenuation oscillation is generated through a coil L, a current flows to the diode D for a half period (t2) of the attenuation oscillation to generate an optical pulse. In bringing the TR to a saturated state during this time, the start voltage across the capacitor is brought into a small value-Vo to reduce the period of optical pulse.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a semiconductor optical device whose voltage-to-current characteristics exhibit three-character negative characteristics that are sensitively affected by external light and which emit light in accordance with the flowing current. Regarding the semiconductor circuit used.

(Prior Art) Conventionally, an example of this type of semiconductor optical device and a semiconductor circuit using the same is described in the literature (IEEE Journal of Qu
antum Electronics, QE-14,
[111 (Nave+wber 1178)].

First, the characteristics of the semiconductor optical device disclosed in this document will be briefly explained. Figure 4 shows the voltage vs. current characteristics of a semiconductor optical device, and the horizontal axis shows the voltage Vd applied to this device.
Also, the current 1d flowing through this element is plotted on the vertical axis.

This element exhibits an S-shaped negative resistance characteristic C)11 including an OFF-stable region, an unstable region m, and an ON-stable region n, and the transition point voltage Vt at the boundary between the OFF-stable region and the unstable region m is It has a high value vt2. Further, when this element is irradiated with light from the outside, the transition point voltage Vt changes from a high value vt2 to a low value Vt, Ic, and therefore has a characteristic CH2 as shown by a broken line in the figure.

Further, this element has a characteristic that in the ON stable region n, it emits light with an amount of light corresponding to the current flowing through the element.

A semiconductor optical device having such characteristics is GaAs.

It is obtained by forming a compound semiconductor such as GaAQAs into a PNPH structure under appropriate manufacturing conditions.

Next, the semiconductor circuit using such a semiconductor optical device disclosed in this document is an optical pulse generator, and the circuit configuration thereof is shown in FIG.

This optical pulse generator l has a capacitor C connected in parallel to a series circuit consisting of a semiconductor optical element having an S-shaped negative resistance characteristic and configured as a diode, and a coil L connected to its anode side and forming an inductance. In addition, one electrode of a capacitor C connected to the coil L is connected to the other electrode of the capacitor C via a first resistor R and a constant voltage power source E. In this case, a constant voltage Voltage power supply E
The anode side electrode of the capacitor C is connected to the terminal e1 of the first resistor R, and the cathode side electrode of the power source E is connected to the terminal e2 of the other electrode side of the capacitor C.

Next, the operation of this conventional optical pulse generator 1 will be explained with reference to FIGS. 4 to 6 (A) to (G). here,
FIG. 6(A) is a curve diagram showing the time waveform of the voltage between the terminals of capacitor C of a conventional optical pulse generator, and FIG. 6(B) is a curve diagram showing the time waveform of the voltage between both terminals of the semiconductor optical device. figure,
FIG. 6(C) is a curve diagram showing the time waveform of the current 1d flowing through the semiconductor optical device.

In the initial state, the voltage Vc across the capacitor C is almost zero or a negative value (-Vf) (-Vf in the example of FIG. 6(A)), and the semiconductor optical device is off (non-conducting). )
From this initial state, charge is accumulated in the capacitor C through the first resistor R1 due to the voltage of the electric current IAE. The voltage Vc across this capacitor C is the initial value -Vf
The voltage increases from the target value to the voltage of the constant voltage power supply E,
When the transition point voltage Vt of the semiconductor optical device is reached (iSS diagram (A) and FIG. 6 (B)), at this time, the device becomes on (conducting) and changes from the off-stable region to the on-stable region n. Move to. In this state, the first resistor R8 and the capacitor C
, operates as a damped oscillation circuit consisting of a coil L and a semiconductor optical element, and thus during a half period of its damped oscillation, the power supply E
The charges in the capacitor C then flow through the semiconductor optical device in the form of a current Id (FIG. 6(C)), causing the device to emit light. After the light is emitted, the characteristics of this element shift from the on-stable region to the off-stable region, and the element turns off.
The voltage Vc across the capacitor C is zero or a negative value (-V
f) and returns to the initial state. This operation is repeated and optical pulses are generated periodically (Fig. 6 (A) to (C)).
).

Under this light pulse period, the charge accumulation time of capacitor C is t7.
When expressed using a time meter 〇 in which a sinusoidal pulse current 1d flows through the element, the following equation is obtained.

Lower = t, +te t7 = -1n(1-(Vt +Vf)/(E+V
f) 1tB = 7C/C, where fLn is a natural logarithm function.

As is clear from this relationship, since the capacitor C of the RC circuit is charged from the power supply E, the voltage Vd between the terminals of the semiconductor optical device changes non-linearly with respect to time during time t7 ( (Figure 6 CB) ), this voltage Vd matches the voltage Vc between both terminals of the capacitor C in the OFF stability region, while in the ON stability region n where current flows, it becomes a low voltage of 1.4V to 2V, There is a sudden change at the boundary between the on and off regions (FIG. 6(B)).

(Problems to be Solved by the Invention) However, in the semiconductor circuit, that is, the optical pulse generator as described above, since Re charging is performed by a constant voltage power supply, the charge accumulation time of the capacitor is shorter than the transition point voltage of the semiconductor optical device. It has the disadvantage that it changes non-linearly. Such non-linear changes have been an obstacle when used as an optical pulse generator or optical power measuring device. Also, since the accumulation and discharge of charge in the capacitor are linear within each on and off period of the semiconductor element, 6. There is a limit to reducing the optical pulse period by reducing the initial voltage value of the capacitor, and there is a need to reduce the influence of temperature changes on the on-region characteristics of semiconductor optical devices on the initial value, and therefore on the optical pulse period. It also had the disadvantage of having limitations.

This invention eliminates the drawbacks of the conventional semiconductor circuits mentioned above, has good linearity of the optical pulse period with respect to the transition point voltage, and can reduce the optical pulse period. The object of the present invention is to provide a semiconductor circuit with little change.

(Means for solving the problem) In order to achieve this object, according to the present invention, a capacitor C is connected in parallel to a series circuit of a semiconductor optical device having S-shaped negative resistance characteristics and an inductance L. One end of the first resistor R1, the other end of which is connected to the anode side electrode of the power source E, is connected to one electrode of this capacitor C coupled to this inductance L, and the other electrode of this capacitor C is connected to In a semiconductor circuit configured to be coupled to the cathode side electrode of the aforementioned power source E, the first main electrode is connected to the other end of the aforementioned first resistor R1, and the control electrode is connected to the other electrode of the aforementioned capacitor C. A transistor Tr is connected and has a second main electrode grounded, a second resistor R2 for coupling the first main electrode to the above-mentioned anode side electrode, and a second resistor R2 for coupling the control electrode to the cathode side electrode. It is characterized by comprising three resistors R3.

In carrying out this invention, the value of this first resistor R1 is
It is characterized in that the value is selected such that the transistor Tr is saturated during the turn-on period of the semiconductor optical device.

(Function) With this configuration, since the circuit including the transistor Tr whose second main electrode is grounded functions as a constant current circuit, a constant current can be supplied from this to the capacitor C via the first resistor R3. The voltage between the terminals of the capacitor C changes linearly, and therefore the optical pulse period changes linearly with respect to the transition point voltage Vt of the semiconductor optical device.

Furthermore, since the first resistor R1 has a resistance value such that the transistor Tr is saturated while the semiconductor optical device is turned on, the initial voltage value of the capacitor C after the semiconductor device is turned on is set to O or It can be a small negative value.

Therefore, the optical pulse period can be reduced and the operating frequency can be increased. Furthermore, the influence of fluctuations in the characteristics of the semiconductor optical device during conduction on the optical pulse period can be reduced.

(Example) An example of the present invention will be described below with reference to one drawing.

FIG. 1 is a circuit diagram for explaining one embodiment of the configuration of a semiconductor circuit according to the present invention.

In this embodiment, a constant current circuit (
(also referred to as a constant current reference source) 2 is connected to form a semiconductor circuit. The transistor Tr is, for example, an npn transistor, whose first main electrode, the collector, is connected to the terminal e, the control electrode, the base, is connected to the terminal e2, and the second main electrode, the emitter, is grounded. . Furthermore, this terminal e is connected to the anode side electrode E+ (note that El also indicates the voltage at this electrode) of a constant voltage voltage 1itH via a load resistor that is a second resistor R2, and on the other hand, the terminal e2 is It is connected to the cathode side electrode E2 of the power source E (note, El also indicates the negative voltage at this electrode) via the base bias resistor which is the third resistor R3. Roughly, a fourth resistor R4 is connected in parallel with the inductance L. In this case, this semiconductor circuit forms an optical pulse generation circuit.

Next, the operation of this circuit will be explained with reference to FIGS. 2(A) to 2(D).

FIGS. 2(A) to 2(D) are time waveform diagrams for explaining the operation of the circuit shown in FIG. 1, including the case where the transistor T is saturated.
(B) is the voltage Vc between the terminals of the capacitor C, (C) is the anode voltage Vd of the diode D, which is a semiconductor optical device, and (D
) is a time waveform diagram of the current Id flowing through this diode D.

Here, in FIG. 2, the voltage Vc of this capacitor C
The time it takes for the voltage to reach the transition point voltage Vt of the diode D is t
1, the time during which the diode D is on is t2, the time from when the diode D is turned on until the transistor Tr is saturated is t3, and the time during which the transistor Tr is saturated is t4, so 12=13+14.

First, since this transistor Tr is a current amplifier, the base current is sufficiently small, so the current flowing through the first resistor R and the current flowing through the third resistor R3 are approximately equal in magnitude, and the Since the base-emitter voltage is approximately constant, approximately 0.6V, the reference current flowing to the terminal e2 via the resistor R is determined by the power supply voltage E and the current flowing through the resistor R1, and from the power supply E to the second resistor. R2
The current supplied through the transistor Tr is shunted to the transistor Tr side, and a constant current I flows through the resistor R1.

Now, the period during which diode D is in the off state 1. , a constant current I is supplied to the capacitor C, and the voltage V at the collector of the transistor Tr increases from the initial value O (Fig. 2 (A)).
And the voltage Vc between the terminals of the capacitor C increases linearly from the initial value of the small value (-Vf) as shown in Fig. 2(B).
), and the voltage Vt of the diode D increases linearly from the initial value -vo (FIG. 2(C)). When the voltage Vc between the terminals of the capacitor C reaches the transition point voltage Vt of the diode D, the diode D turns on, so the capacitor C
starts discharging and a damped oscillation occurs in the diode D through the coil L forming an inductance, and each voltage is suppressed (period tz in Fig. 2 (A) to (C)), and the half cycle of this damped oscillation During the period , a current flows in a pulsed manner (FIG. 2 (b)), and a light pulse is generated from the diode D.

During the period t2 during which the diode D is on, the voltage Vc between the terminals of the capacitor C decreases from the voltage Vt to O or -VF (FIG. 2(B)), and the voltage Vd of the diode D decreases from the transition point voltage Vt to 1. It changes to 4 to 2 V, and becomes -VO at the start of the next turn-off, that is, when charging of the capacitor C starts (Fig. 82 (C)).

During the time t3 of the diode D, the collector voltage V of the transistor Tr is maintained at a voltage larger than the voltage Vc between the terminals of the capacitor C by a constant voltage R, I due to the damped oscillation of the diode D, and a light pulse is generated. A constant current is supplied to the device 1, but there is a period t during which the transistor Tr reaches saturation.
4, the collector voltage V cannot supply a constant current (FIG. 2(A)).

During this time t4, the resistance R is added to the damped oscillation circuit, so the damping increases and the period t4 of the damped oscillation becomes slightly longer than the period t3 (=ycE6/2) (to
≧L3) is well known, and as a result, the turn-on time t2 becomes slightly longer.

The fourth resistor R4 connected in parallel with the coil L is used to absorb extremely fast damped vibrations that may occur immediately after the diode D is turned off due to the small junction capacitance of the diode D and the coil L. It was established.

By the way, the time during which diode D is turned off is 1. The charge gradually accumulated in the capacitor C is discharged within a relatively short time t2 by turning on the diode D, and a pulse current Id flows through the diode D (Fig. 2 (D)).
), so if we gradually reduce the value of the first resistor R, we get
The transistor Tr becomes saturated, and under that condition, an excessive current flows through the transistor Tr. Therefore, the optical pulse period T
can be made shorter.

This point will be explained below with reference to FIG. Figure 3 shows capacitor C in non-saturated operation of transistor Tr.
FIG. 3 is a time waveform diagram showing the voltage Vc between terminals of FIG. The voltage Vc across the capacitor C starts discharging from the transition point voltage Vt due to conduction of the diode D, a pulse current 1d flows through the diode D, and when this voltage Vc finally becomes -Vf, the transistor Tr is not saturated. In order to do so,
If the resistance value of the first resistor R is R, then a resistance value R that satisfies the relationship R>Re RCI>VF, where Rc is a constant value, may be selected.

When this transistor T" performs a non-saturated operation, the optical pulse period T is a period te during which the voltage Vc between the terminals of the capacitor C linearly increases due to the constant current I.

The period is the sum of the period 6 and the half period of the damped oscillation in which the pulse current ld flows through the coil L to the diode D. That is, T=t5+t.

It is expressed by the relationship t,=C(Vt+Vf)/It,=7n lights. The time t5 during which charge is accumulated in the capacitor C by the constant current I varies linearly depending on the transition point voltage Vt of the diode D.

If this transition point voltage Vt changes greatly due to light reception, it is necessary to bring the voltage vf into a sufficiently negative direction in order for the diode D to turn off completely after turning on. If the value is large, it takes time to accumulate the charge in the capacitor C and raise it to the transition point voltage Vt, which has the disadvantage that the optical pulse period T cannot be shortened.

The reason why the optical pulse period T cannot be shortened in this way is that the charge in the capacitor C is discharged in a linear circuit due to the damped oscillation during the turn-on period of the diode D. Therefore, this damped oscillation If the circuit has a nonlinear circuit configuration, the pulse period T can be improved.

Therefore, by selecting the resistance value R of the first resistor R as R<Rc RcI=VF, the resistance value R can be made smaller than Rc, and the capacitor C can be set to an initial value of 0 or a negative value (-V
When the voltage is D, the collector voltage of the transistor Tr becomes Ov, so the transistor Tr is saturated. Therefore, at this time, since the collector voltage V cannot become negative, a constant current cannot be supplied through the first resistor R, and the transistor Tr becomes a voltage source with zero voltage. In this case, the value R of the first resistor R is important, and the charge is transferred with the time constant of CR. As a result, the voltage Vc between the terminals of the capacitor C, after the diode D is turned on, initially undergoes a damped oscillation accompanied by the supply of constant current from the constant current circuit 2, but then the transistor T' saturates. So,
Since the resistor R changes into a damped vibration with a low resistance added, the voltage is suppressed and the initial voltage value of the capacitor C is reduced to a small value -v
o, and therefore, the optical pulse period T can be made small.

Further, the initial voltage value -vf or -vo of the capacitor C obtained by the damped oscillation when the diode, ie, the semiconductor optical device, is turned on depends on the characteristics of the damped oscillation when the semiconductor optical device is turned on. In other words, since the conduction resistance of a semiconductor optical device changes with temperature, the damped oscillation caused by deviation from a pure LC resonant circuit depends on temperature changes, but by setting the initial voltage value to a small -v0,
This has the advantage that the influence of the conduction characteristics of the semiconductor optical device on the initial voltage value can be reduced.

It is clear that the present invention is not limited to the embodiments described above. For example, the transistor T" may be replaced with a PnP transistor, and appropriate changes may be made accordingly if necessary.

(Effects of the Invention) As is clear from the above explanation, according to the semiconductor circuit according to the present invention, since a constant current circuit using a transistor is provided, the optical pulse period is variable with respect to the transition point voltage of the semiconductor optical device. can be changed linearly. Furthermore, by selecting the resistance value of the first resistor to a value that provides a period during which the transistor is saturated while the semiconductor optical device is turned on, it is possible to obtain the effect of changing the resistance of the transistor like a switch. The initial voltage value of can be set to 0 or a small negative value,
Therefore, the effect of reducing the optical pulse period can be obtained.

Furthermore, this makes it possible to increase the operating frequency and reduce the influence of fluctuations in the characteristics of the semiconductor optical device during conduction on the optical pulse period.

Since the semiconductor circuit of the present invention has such advantages,
It is possible to widen the operating range of optical pulse generators, optical power measuring instruments, etc., and thereby expand the range of applications.

Furthermore, the same effects as described above can be achieved by appropriately modifying the circuit configuration described above.

[Brief explanation of drawings]

Figure m1 is a circuit diagram showing a positional example of the configuration of a semiconductor circuit according to the present invention, and Figures 2 (A) to (D) are time waveform diagrams for explaining the present invention in detail. Fig. 3 is a time waveform diagram for explaining the present invention, Fig. 4 is a characteristic curve diagram for explaining the characteristics of semiconductor optical devices used in the present invention and conventional semiconductor circuits, and Fig. 5 is a conventional semiconductor circuit. FIG. 3 is a circuit diagram showing the configuration of. FIGS. 6A to 6C are time waveform diagrams for explaining the operation of a conventional semiconductor circuit. l... Optical pulse generator, 2... Constant current circuit Tr.
...Transistor, D...Semiconductor optical device C...
Capacitor, L...Inductance R,...
・First resistor, R2... Second resistor R3... Third resistor, R4... Fourth resistor El... Anode side electrode of the power source R2... Cathode side electrode of the power source el+62... Terminal . Patent applicant: Oki Electric Industry Co., Ltd.,・no・−1 Agent: Patent attorney Takashi Ogaki 11′″・z
°' Figure 1 Figure 2 Figure 4 Figure 6 Procedural amendment (method) 3 Relationship with the person making the amendment Patent applicant address (〒-105) 1-7-12 Toranomon, Minato-ku, Tokyo Name (029) Oki Electric Industry Co., Ltd. Representative Nankai Hashimoto 4 Agent 170 Tt (988) 5563 Address 905 Ikebukuro White House Building, 1-20-5 Higashiikebukuro, Toshima-ku, Tokyo Name (8541) Patent Attorney Takashi Ogaki 5 Date of amendment order: March 26, 1985 6. Subject of amendment: Detailed explanation of the invention in the specification, column 7. Contents of amendment: Amended as shown in the attached sheet. (1) Page 2 of the specification, line 1O (7) r (IEE
Journal of EJ
Taong Tam Electronics (corrected as IEEEJ. Procedural amendment November 29, 1980)

Claims (1)

[Claims] 1. A capacitor is connected in parallel to a series circuit of a semiconductor optical device having S-shaped negative resistance characteristics and an inductance, and one electrode of the capacitor coupled to the inductance is connected to the other end. A semiconductor circuit configured such that one end of a first resistor is connected to an anode side electrode of a power source, and the other electrode of the capacitor is connected to a cathode side electrode of the power source. a transistor having a first main electrode connected to one end thereof, a control electrode connected to the other electrode of the capacitor, and a second main electrode grounded; and a transistor for coupling the first main electrode to the anode side electrode. A semiconductor circuit comprising two resistors and a third resistor for coupling the control electrode to the cathode side electrode. 2. The semiconductor circuit according to claim 1, wherein the value of the first resistor is selected such that the transistor is saturated during a turn-on period of the semiconductor optical device.