JPH02179116A - Optical input signal processing circuit - Google Patents

Abstract

PURPOSE:To obtain performance adapted effectively to various applications by connecting a base modulation type bipolar transistor(TR) to an output side of a photodetector. CONSTITUTION:A photodetector 2 converting an optical signal from a light projecting means 1 and a base modulation type bipolar TR 4 having a negative resistance characteristic with a voltage comparate function and a current comparate function are provided and the base modulation type bipolar TR 4 is connected to the output of the photodetector 2. Then the voltage comparate function and the current comparate function of the base modulation type bipolar TR 4 are utilized for the circuit processing of a photodetection device. Thus, various functions such as a bistable output with a hysteresis and an output as a memory operation are provided with simple circuit constitution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an optical input signal processing circuit that converts an optical signal from a light projecting means into an electrical signal and outputs the electrical signal. This invention relates to an optical input signal processing circuit using a base modulation type Ibora transistor.

[Prior art and its problems] Conventionally, a light receiving device (2) such as a photodiode or a phototransistor receives an optical signal from a light projecting means (1), converts it into an electrical signal, and outputs the signal. As input signal processing circuits, circuit configurations as illustrated in FIGS. 17, 18, and 19 are known. The optical input signal processing circuit illustrated in FIG. 17 receives an optical signal from a light emitting diode (LED) or the like with a photodiode (PDS),
It is amplified by a transistor (Tri). In this example, the resistor (r2i1) determines the threshold voltage and directs the leakage current to the transistor (Tr
It also prevents it from flowing to the +) side. The optical input signal processing circuit illustrated in FIG.
Phototransistor (PTr9) instead of diode
In order to obtain high sensitivity, In both of these two circuit examples, if the resistances (r2&) and (21+) are increased in order to increase the threshold and hold level and reduce the leakage current flowing into the transistor (Tr+) or (Tr2) side, the leakage current will flow into the resistor. The optical input current increases and the sensitivity decreases.On the contrary, the resistance (r2B), (r28)
Increasing increases the sensitivity, but has the disadvantage of increasing leakage current and slowing the switching speed.Furthermore, when these two circuit examples are used for switching, there is no hysteresis, so chattering etc. There were some problems.These problems should be solved (
The proposed optical input signal processing circuit illustrated in FIG. 19 has a circuit configuration that uses a Schmitt trigger circuit (3) to shape the waveform.

The optical input signal processing circuit illustrated in FIG.
Although the problems of the optical input signal processing circuits illustrated in FIGS.
This has problems such as high cost and increased current consumption.

[Problem to be Solved by the Invention 1] Therefore, the present invention solves the various problems seen in the optical input signal processing circuits in the prior art described above, and provides an optical input signal processing circuit with performance that is effectively applicable to various fields. The purpose of this invention is to provide a processing circuit.

[Means for Solving the Problems] To achieve the above object, the present invention specifically provides an optical input signal processing circuit that converts an optical signal from a light projecting means into an electrical signal and outputs the electrical signal. , a light-receiving element that converts an optical signal into an electrical signal, and a base-modulated bipolar transistor having a negative resistance characteristic and a voltage comparison function and a current comparison function, and the base-modulation bipolar transistor is connected to the light-receiving element. An optical signal processing circuit is configured by connecting to the output side of the element.

[Embodiment 1 of the present invention] Hereinafter, a base modulated bipolar transistor (base modulation type bipolar transistor) having negative resistance characteristics according to the present invention will be described.
onBipolar Transistor: BA
An optical input signal processing circuit using an optical input signal processing circuit (abbreviated as MBIT) will be described in detail based on several specific embodiments shown in the drawings.

In this invention, an optical input signal processing circuit which is a first wing-shaped embodiment is shown in FIG. The optical input signal processing circuit shown in FIG.
The optical signal is received by I), the optical signal is converted into an electrical signal, the electrical signal is amplified by 8AMBIT (4), and the waveform is shaped and output. Before explaining the operating principle of the optical input signal processing circuit shown in Fig. 1, Fig. 2 shows an example of BAMBIT's base grounding characteristics as an example of static characteristics, and Fig.
Figure 4 shows an example of grounded emitter characteristics using the base voltage vBE of AMBIT as a parameter, and the base current of RAMBIT! Examples of grounded emitter characteristics using B as a parameter are shown below. Regarding the structure of BAMBIT itself and its operating principle, please refer to the patent application filed by the same applicant, Patent Application No. 63-196.
It is described in detail in No. 627. On the other hand, Figures 2 and 3
In each characteristic example shown in Figures and Figure 4, VCE (OFF) = VBE + VCB (OPF) -...
---The relationship (1) holds true, and the negative resistance value RN in the negative resistance region of BANBIT is as follows. Here, hi is a current amplification factor for the output current (lc+lG) in the active region of BAI'1BIT.

FIG. 5 is an operational explanatory diagram illustrating the circuit operation of the optical input signal processing circuit according to the present invention shown in FIG. Based on this figure, the circuit operation of the optical input signal processing circuit shown in FIG. 1 will be explained. In the circuit shown in Figure 1, when the photodiode (PDI) receives an optical signal, the photocurrent of the photodiode (PDI) flows through the resistor (rl), which is the anode of the photodiode and the base of RAMBIT. The potential VP at a certain P point increases. In this case, in the case where an ordinary linear transistor as shown in Fig. 17 is connected to the output side of the photodiode (POI), the P' point reaches approximately 0.7V, and the transistor (Tri) A photocurrent flows into the base, is amplified, and appears as the output of the transistor (Tr l ). On the other hand, the photodiode (P, DI
), when RAMBIT is connected to the output side of BAMBIT, the curve that gives the output characteristics of BAMBIT for a certain amount of input current is obtained as a curve, as shown in Figure 5, and the resistance (r2)
The intersection with VCE =
Vcc, and no output current flows. Furthermore, when optical input is applied, the potential vP at point P, which is the base voltage of RAMBIT, increases. Then, the characteristic curve of BAMBIT changes according to the base voltage dependence, as shown in FIG. The output characteristics of BAMBIT for input are 8 curves from 2 points to point
B(OFF)=VCC, in other words, the base voltage vP of RAMBIT as the circuit example in FIG. 1 becomes VP=
VBE=VCC-ycB(OFF)+:: reached, hot.
The photocurrent of the diode (2 ports 1) flows into the base of BAMBIT, and the amplified output current (lc+IQ) of RAMBIT flows out through the load resistor (r2).

Then, the voltage at the collector of BAMBIT decreases, and R
Since AMBIT has negative resistance characteristics, the output current (IC+IQ) increasingly flows in a manner that reverses the load resistance (r2). Due to this positive feedback action, the intersection with the load line instantly moves from point X to point 7. In other words, the switch is suddenly turned on due to the voltage comparison operation.

Furthermore, even if the optical input is made stronger, the saturation region of RAMBIT intersects with the load resistance (r2), so the output hardly changes anymore. At this time, since the potential at point P is conductive between the base and emitter as in a normal transistor, the rising voltage between the base and emitter drops to about 0.7V.

Next, a case will be described in which the optical input is turned on and then weakened. As the optical input becomes weaker, the output characteristic curve of BAMBIT changes depending on the input current intensity. However, even if the optical input becomes weak, the switch is not turned off unless it reaches the C curve, and the intersection with the load resistance (r2) is at the appropriate side of the V point. Then, the optical input is even weaker than that of the C curve (as the base Sanno 1/p decreases and the base current decreases, the BAM old T and the load resistance (r2) become RAMB
When IT is saturated or in some active region, they no longer intersect (then the intersection returns to point X again and RAMBIT is switched off. In other words, BAMBIT's current comparator function causes it to switch off with hysteresis. In addition, when the switch is turned ON, the 7th point reaches the X point and attempts to turn the switch, but the 8th
If the negative resistance value IRNI on the curve is compared with the load resistance (r2), and IRNI<r2, the current will be compared, the intersection will remain near the X point, and the switch will not turn on.
Maintain the OFF state. Here, 1llNl for the load
The base input current required to satisfy <r2 and turn on the switch is hereinafter referred to as base holding current. As shown below, due to the optical input in Figure 1, the potential VP at point P increases due to the resistor (1) and reaches VP = VCC - VCB (OFF), and the input terminal value at that time is the base holding current value. When the switch ONt, the optical input is the load resistance (r2
), the switch
When turned OFF, bistable and high-speed input/output characteristics with hysteresis as shown in FIG. 6 can be obtained. The embodiment circuit shown in FIG. 1 is suitable for optical transmission and the like. Moreover, if operated under RNl<r2, highly sensitive linear amplification is achieved.

A second embodiment circuit is shown in FIG. In this example, a phototransistor (PTrl) is used as the light receiving element (2). This circuit is the same as the circuit of the first embodiment (a bistable switch output with hysteresis can be obtained with respect to optical input. In Fig. 7, a phototransistor (
PTrl) and BAMB I T are connected in Darlington, so high output can be obtained and it is suitable for interbrars, solid state relays, etc. Here, the circuits shown in FIGS. 1 and 7 have the potentials VP and V at point P and point 0 (7).
Since there is no switch/ONL unless Q becomes l:l/CC-vca(opp), resistor (r+), (r3)
For each, one with high resistance can be selected. After the switch ONL, the forward voltage between the base and emitter of both 'jp and VQ drops to about 0.7V, so the amount of optical input current flowing into the resistors (rl) and (r3) is small. Therefore, a high switch/ON level can be obtained without reducing the output.Also, since the switch/ON level can be set high, leakage current can be reduced without reducing the output.

The embodiment circuit shown in FIG. 8 is different from the embodiment shown in FIG.
6) is added to the BANBIT base, suppressing excessive input after the switch is turned on, and also adjusting the hysteresis width.

The example circuit shown in Fig. 9 is the same as the example circuit shown in Fig. 7, but with rl>>j9 connected to enable bistable switching operation with two terminals, and connected with Darlington, various detection devices and Suitable for solid state relays, etc.

The embodiment circuit shown in FIG. 10, contrary to the embodiment circuit shown in FIG. 7, is an example of a circuit that is always on and receives light, especially when it is switched off. The current flowing into the base of BANBIT through the resistor (rlo) is transferred to the phototransistor (PT).
r4) by shining light on it.

Then, as explained in FIG. 5, the switch is turned off by reducing the base current below the base holding current with respect to the load resistance (rl). Also, -dan switch
After turning off the switch and turning it on, it is sufficient to weaken the optical input until the potential at point R reaches VR = VC (! - VCB (OFF).Furthermore, the normally on processing circuit in Fig. 10 This can naturally be applied to FIG. 1 as well.

The example circuit shown in FIG. 11 is a combination of the circuits shown in FIGS. 7 and 10, and can be set and set by optical input.
This allows for resetting. First, the potential v at 8 points
S is vS = V CCX fl 3 / j +
As long as the state of 2 < vCC-l/CB (OFF) is maintained, the switch remains OFF due to the characteristics of the DAM old T. Therefore, light enters the phototransistor (PTrS), and the potential VS at 8 points is set to vs>vcc-%1cs(ar
p) Do d. Then, if the input through the resistor (rl2) and phototransistor (PTrS) exceeds the base holding current value for the resistor (rl4), the switch will suddenly switch off.
Turn on. Even if light is cut off from entering the phototransistor (PTrS), the state of the switch ONL continues to be memorized as long as the base holding current value or more is maintained only by the input through the resistor (rl2). Resetting is performed quickly by reducing the base current passing through the resistor (rl2) to RAMBIT to below the base holding current value for the load resistor (1 port) by inputting light to the phototransistor (PTrs), and 8 points. The potential vS is again I/5=
Return to VCCXj13/j12+j+3.

The example circuit shown in FIG. 12 is different from the example circuit shown in FIG. 1 in that the potential at one point is raised from the beginning using a constant voltage circuit (5) etc. in order to further increase the sensitivity and switching speed. The resistor (rl5) can be made smaller than the resistor (rl), and high speed and high output can be obtained.

The example circuit shown in FIG. 13 first passes through the resistor (rl7) and sets the base current input to the base of the DAM old ■ below the base holding current value with respect to the load resistor (rl8), and then By setting T to OFF state and adding the optical input current value from the photodiode (Fluff), BAMBIT can be switched on and switched off using only the current comparator according to the characteristic curve group shown in Figure 4. This is an example of a circuit.

The embodiment circuit shown in FIG. 14 is the same as the circuit shown in FIG. 7, except that a load resistor (rl+) is also inserted in the emitter.

The embodiment circuit shown in FIG. 15 has a two-terminal connection similar to that shown in FIG. 9, but has an emitter load (r23) instead of the collector load. In this case, the operating principle of switching ON is slightly different from the circuit example shown in FIG. 9. In FIG. 15, r22>>(23), and the potential vu at the 0 point increases due to optical input without being affected by the resistance (r23).

Then, due to the voltage comparison function of BAMBIT, the voltage VU is changed to I/u=l/cc-vca(opp)l:J, and the optical input current flows into the base of BAMBIT (7).

However, in this case there is no load on the collector, so
The collector potential is l/cc, and the base potential VU is also y
It becomes near cc-vCB (OFF). However, V
The potential VV at the point is the BAMBIT output current (lc +
to) flows as hFE times the base current IB, so it begins to rise. Due to this increase in the potential %Iv at point V, the resistance (r2
2) The number of optical input terminals flowing to the side is reduced.

Base current IB to RAM old T increases. Then, the output current increases more and more, and the potential VV at point V further increases. Due to this positive feedback action, the BAM old T is switched on instantly. In the case of switch OFF, the current comparator function of <RAMBIT is used as in the previous example.

The embodiment circuit shown in FIG. 16 is an example of a circuit that enables high-speed pulse oscillation using an optical input signal. Photo diode (
When PO4) receives an optical input signal, the capacitor (C1)
is filled, and the potential vw at the opposite point rises. Then, the same as in the embodiment described above (the potential vw at point W is vw>vCC-V
It reaches CB (OFF), voltage is compared, and BAMB
Discharge through the resistor (r24) to the base of IT and BA
MBIT is switched on. During the discharge process of the capacitor, when the sum of the discharge current and the input current of the photodiode (PO3) is less than the base holding current value for the resistor (r26), the BAM old T is in the ON state. When the discharge continues and the current drops below the base holding current value, the current is compared and BAMBIT is switched OFF.
, again the optical input current of the photodiode (2 ports 4) charges the capacitor (C1). Through this process, RA
MBIT performs high-speed pulse oscillation operation. In this oscillation circuit example, the pulse width and oscillation frequency can be changed by a capacitor (C1) and a resistor (<r24), and the oscillation frequency can also be changed by the optical input intensity to the photodiode (PO4).

As described above, by combining the light receiving element (2) and RAM old ■ (4), BA? By using the voltage comparator function and current comparator function of I-T, various bistable circuits, memory circuits, oscillation circuits, etc. can be easily assembled. In addition, it is possible to replace a diode with a photo-transistor, or to replace a photo-transistor with a photo-diode, and it is also possible to use a light-emitting diode as well as sunlight as the light emitting means (1). This is not limited to just an example, and can be applied to various combinations. Furthermore, this invention can be applied to other sensors that use magnetism instead of light receiving devices, and can also be applied to general signal conversion circuits. It can also be applied to applications such as changing the characteristics and changing the threshold level.

E Effect 1 of the Present Invention The optical input signal processing circuit of the present invention having the above-described configuration exhibits a number of effects shown below.

(1) A bistable output with hysteresis with respect to optical input can be obtained with an extremely simple circuit configuration and no current consumption.

(11) High-speed switching operation can be obtained with an extremely simple circuit configuration.

(ii) Even with two terminals, a bistable output with hysteresis can be obtained with an extremely simple circuit configuration.

(iv) With an extremely simple circuit configuration and low current consumption, it is possible to operate the memory even with large currents.

(v) A bistable output with hysteresis can be obtained even in normal/ON operation.

(vi) Leakage current, which was a problem when using phototransistors as in the past, is almost eliminated.

(vi) High frequency oscillation is possible with an extremely simple circuit configuration.

As described above, by using BAMBIT's voltage comparator function and current comparator function in the circuit processing of photodetector devices, various outputs such as bistable output with hysteresis and output as memory operation can be achieved with a simple circuit configuration. It can have many functions and its effects are great.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a concrete first embodiment of the optical input signal processing circuit according to the present invention, FIG. 2 is a base grounding characteristic curve diagram of a base modulation type bipolar transistor, and FIG. , a common emitter characteristic curve diagram when the base voltage of a base modulated bipolar transistor is taken as a parameter, FIG. 4 is a common emitter characteristic curve diagram when the base current of a base modulated bipolar transistor is taken as a parameter, 1 is an operation explanatory diagram for explaining the circuit operation of the example circuit shown in FIG. 1. FIG. 6 is an input/output characteristic diagram of the example circuit shown in FIG. 1. FIGS. 7 to 16 are circuit diagrams showing second to eleventh embodiments of the optical input signal processing circuit according to the present invention, and FIGS. 17 to 19 are circuit diagrams showing the first to third examples of the conventional optical input signal processing circuit. FIG. (1) Light projecting means (2) Light receiving element (4) Base modulation bipolar transistor: AMBIT (PDI) ~ (P port 4) ...Photodiode (PTr + ) ~ (PTr8) ...Phototransistor<"1" ~ (r2s) ...Resistance (C
I)・・・・・・Capacitor

Claims (1)

[Claims] An optical input signal processing circuit that converts an optical signal from a light projecting means into an electrical signal and outputs the same, the circuit includes a light receiving element that converts the optical signal into an electrical signal, and a negative polarity having a voltage comparison function and a current comparison function. 1. An optical signal processing circuit comprising: a base modulation type bipolar transistor having resistance characteristics; said base modulation type bipolar transistor being connected to the output side of said light receiving element.