JPH0992869A - Received light amplifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a current-voltage conversion amplifier circuit from being saturated if a high-intensity light is received, by taking a current from the other end of a photodetector element and reducing this current less than an input photocurrent applied from one end of this element to the amplifier circuit. SOLUTION: A received light amplifier circuit has a photodetector element 100 and current-voltage conversion amplifier circuit 3. A resistor R1 is inserted between the anode of the element 100 and ground and current mirror circuits 1 and 2 are connected to the cathode and the anode of the element 100. Utilizing a current from the cathode of the element 100 and mirror circuits 1 and 2, a reverse-phase current Ipda is made and added to the input of the circuit 3, thereby reducing the photocurrent Ipda. Thus, a current Iin inputted to the circuit 3 is the difference current between a photocurrent Ipd produced by the element and current Ipda, this reducing the saturation of an input transistor Q101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-receiving side light-receiving / amplifying device used for optical space transmission between devices such as personal computers and portable information terminals, and particularly for optical transmission by the IrDA system.

[0002]

2. Description of the Related Art In recent years, IrDA has been used as an optical space transmission method between devices such as personal computers and portable information terminals.
(Infrared Data associative
The n) method has been standardized, and various attempts have been made to speed up signal transmission particularly for use in image data. Hereinafter, a conventional photoreceiver / amplifier circuit compatible with the IrDA system will be described with reference to FIGS.

FIG. 15 is an equivalent circuit diagram of an infrared receiver including a conventional photoreceiver / amplifier circuit, FIG. 16 is a concrete circuit diagram of the photoreceiver / amplifier circuit of FIG. 15, and FIG. 17 is a waveform diagram of each part of FIG.

Conventionally, a receiver used for infrared data transmission converts a photocurrent generated by infrared light received by a light receiving element 100 into a voltage by a current-voltage conversion amplifier circuit 101, as shown in FIG. The amplifier 102 amplifies the signal and the comparator 103 reproduces the pulse.

More specifically, the photocurrent I _pd generated by the light receiving element 100 is converted by the feedback resistor Rf in the current-voltage conversion / amplification circuit 101 into a voltage having an opposite polarity and an absolute value proportional to Rf. Here, the output Vha of the current-voltage conversion amplifier circuit 101 is represented by Vha = −I _pd × Rf (101).

The output Vha is further amplified by the amplifier 102 and becomes the output V _2nd . The waveform of the output V _2nd is the threshold level V of the preset comparator 103.
The comparator output is inverted at the timing that crosses th,
The pulse signal V _O is reproduced.

By the way, conventionally, a circuit is devised so that a wide operation range can be secured for the photocurrent I _pd .

First, as shown in FIG. 15, the feedback resistor Rf
A transistor Q100, which is diode-connected in parallel, is added to this so as to prevent the amplifier from being saturated even when a large photocurrent I _pd is input. Also, as shown in FIG.
In order to increase the DC bias voltage of the input and extend the operating range of Vha, a diode-connected transistor Q102 is inserted in the emitter of the input transistor Q101. In the circuits of FIGS. 15 and 16, the operating range of Vha is as follows.

Assuming that the current amplification factor of the transistor Q101 is sufficiently large: Vha = Vin = 2 × Vbe = 1.4V (102) where Vbe is the base-emitter voltage of Q101 and Q102. It is set to 7V.

When I _pd is generated, Vh
Although the voltage of a decreases, it is clamped by the diode Q100, so that Vha MIN. becomes Vha MIN. = 1.4V−0.7V = 0.7V (103). Therefore, the operating range ΔVha of Vha is ΔVha = Vha-Vha MIN. = 1.4V-0.7V = 0.7V (104).

In the circuit of FIG. 16, Q103 is an output stage transistor, and I ₁ and I ₂ are constant current sources.

According to the circuit described above, an inverted signal Vha as shown in FIG. 17 (b) is obtained for an input signal as shown in FIG. 17 (a), and V _2nd as shown in FIG. 17 (c) is obtained. As a result, the output signal V _o is finally obtained as shown in FIG.

[0013]

Conventionally, the operation range of the amplifier circuit is expanded and the range of the received light amount of the input light amount is widened by the above-described method. However, even in this circuit, there is a problem that the following phenomenon occurs when the amount of light is large, and the pulse signal cannot be normally reproduced. Here, the case where a large amount of light is input includes, for example, a case where signals are transmitted between information portable terminal devices and the devices are very close to each other. Below, the waveform diagram to explain the problem,
This will be specifically described with reference to FIG.

First, in FIG. 16, when the photocurrent I _pd exceeds the constant current amount of the constant current source I ₂ , there is no path for I _pd to flow into the base of the transistor Q101.
As a result, the transistor Q101 enters a deep saturation state. Therefore, the transistor Q101 does not recover from saturation even after the light receiving state is stopped and I _pd no longer flows.
As a result, as shown in FIG. 18 (b), the waveform of Vha is blunted and stretched, and it is about to come into contact with the next pulse. Therefore, as shown in (c), the waveform of V _2nd crosses the threshold level of the comparator. , As shown in (d), V _O
Shows an example in which is low level for a long time.

This phenomenon becomes more remarkable as the photocurrent I _pd is larger than I ₂ which is the bias current of the output section of the current-voltage conversion amplifier circuit 101, and the higher the frequency of the received light signal, the greater the influence. .

If I ₂ is around 100 μA, the above problem occurs when the photocurrent I _pd is several hundred μA or more. In the field of infrared data communication targeted by the present invention, it is a condition that photocurrent can be generated up to the order of several mA, and a countermeasure against pulse blunting when a large amount of light is input is an unavoidable problem.

Particularly, even in the IrDA system, this problem becomes important when the transmission speed is 4 Mbps or more. The IrDA data transmission method is currently I
rDA1.0 (SIR) method and IrDA1.1 (FI
R) system, there are two systems, and the transmission rates targeted by the former and the latter are 2.4 kbps to 115.2 kbp.
s, and 9.6 kbps to 4 Mbps.

19 (a) and 19 (b) respectively show Ir.
It is a signal waveform diagram of DA1 and IrDA2. FIG.
As shown in (a), the signal transmission of IrDA1 is "0" if the signal is HIGH during 3 / 16T of the signal unit T, and "1" if it is LOW. Therefore, even if the signal is continuous with "0" and "0",
There is a relatively large gap between the two.

On the other hand, as shown in FIG. 19B, in the case of IrDA2 signal transmission, 500 ms is set as one unit of the signal transmission, and this one unit is divided into four equal parts to obtain the first 125.
When it becomes HIGH in order from ms, (00), (0
The meanings of 1), (10), and (11) are given. Therefore, if the data of (11) extends backward, there is a possibility of misidentification such as determining that the next data is (00) although it is (01), for example.

As described above, in infrared data communication,
Especially for image data transmission with a large amount of data (IrDA
1.1) (4 Mbps, etc.) tends to cause a problem that a signal cannot be ideally reproduced.

Therefore, an object of the present invention is to reliably reproduce a signal without causing circuit saturation or the like during current-voltage conversion even when a large amount of light is incident when the amount of data is large as in image data transmission. It is to provide a highly reliable light receiving and amplifying device.

[0022]

In order to achieve the above object, the first aspect of the present invention comprises a light receiving element and a current-voltage conversion amplifier circuit for amplifying a photocurrent generated in the light receiving element. In a photoreceiver / amplifier circuit in which the photocurrent of the photoreceiver is input to the current-voltage conversion amplifier circuit from one end of either the anode or the cathode of the photoreceiver, a current is also taken out from the other end of the photoreceiver, and the current component is It is characterized in that it is reduced from the photocurrent inputted from one end of the light receiving element to the current-voltage conversion amplifier circuit.

According to a second aspect of the present invention, in the light-receiving / amplifying circuit according to the first aspect, a current component extracted from the other end of the light-receiving element is input to the current-voltage conversion / amplifying circuit from one end of the light-receiving element. It is characterized in that it is configured to be smaller than the above.

According to a third aspect of the present invention, in the light receiving / amplifying circuit according to the first aspect, a first current mirror formed of a transistor is provided at the other end of the light receiving element different from the input end to the current / voltage converting / amplifying circuit. The input part of the circuit is connected, and the output part of the first current mirror circuit is connected to the input part of the second current mirror circuit composed of a transistor having a polarity opposite to that of the first current mirror circuit. The output part of the current mirror circuit is connected to the input end of the light receiving element to the current-voltage conversion amplifier circuit.

According to a fourth aspect of the present invention, in the light receiving and amplifying circuit according to any one of the first to third aspects, a branch line is provided at the input end of the light receiving element to the current-voltage converting and amplifying circuit, and a branching resistor is connected to the resistor. The photocurrent to the current-voltage conversion amplifier circuit is shunted according to the ratio of the impedance of the current-voltage conversion amplifier circuit.

According to a fifth aspect of the present invention, in the photoreceiver / amplifier circuit according to the third aspect, at least the current output value of the first current mirror circuit among the first and second current mirror circuits is higher than the current input value. It is characterized by being set small.

According to a sixth aspect of the present invention, in the light receiving and amplifying circuit according to the third aspect, a resistor is provided between the other end of the light receiving element to which the first current mirror circuit is connected and the power supply or GND, It is characterized in that the first and second current mirror circuits are operated only when the current value is equal to or more than a predetermined current value.

According to a seventh aspect of the present invention, in the light receiving and amplifying circuit according to the third aspect, the other of the light receiving element is provided between the output section of the first current mirror circuit and the input section of the second current mirror circuit. A delay circuit for delaying the phase of the current extracted from the end from the phase of the current input to the current-voltage conversion amplifier circuit from one end of the light receiving element is provided.

According to an eighth aspect of the present invention, in the light receiving and amplifying circuit according to the seventh aspect, the delay circuit includes a capacitor and a resistor whose one ends are commonly connected, and the connection point of the delay circuit is the first current mirror circuit. Is connected to the output of the first current mirror circuit and the resistor is connected to the output of the first current mirror circuit.
Of the current mirror circuit, and the other end of the capacitor is connected to GND or a power supply.

According to a ninth aspect of the present invention, in the light receiving and amplifying circuit according to any one of the seventh and eighth aspects, the light receiving and amplifying circuit is provided between the light receiving element and the current and voltage converting and amplifying circuit at an input portion of the current and voltage converting and amplifying circuit. And a saturation prevention circuit for preventing saturation of the input stage transistor, the saturation prevention circuit comprising a saturation prevention resistor having one end commonly connected and a saturation prevention transistor having a base and an emitter short-circuited. The connection point of the saturation prevention circuit is connected to the light receiving element, the other end of the saturation prevention resistor is connected to the input part of the current-voltage conversion amplifier circuit, and the other end of the saturation prevention transistor is the transistor of the input stage. It is characterized by being connected to the collector of.

According to a tenth aspect of the present invention, in the light receiving and amplifying circuit according to any one of the seventh and eighth aspects, an input stage transistor provided in an input section of the current-voltage converting and amplifying circuit prevents saturation of the input stage transistor. The saturation prevention transistor is connected, the emitter and the base of the saturation prevention transistor are connected to the input and output of the current-voltage conversion amplifier circuit, and the collector is connected to the GND or the power supply. .

The operation of each solving means will be described below.

According to the first aspect, the photoelectric flow rate generated in the light receiving element and input to the current-voltage conversion / amplification circuit is reduced. Therefore, even when a large photocurrent (that is, a large amount of received light) is generated, As described above, it is possible to avoid the problem that accurate signal reproduction cannot be performed due to the saturation generated in (the input stage transistor of) the current-voltage conversion amplifier circuit.

Here, if the current component to be deleted from the photocurrent input to the current-voltage conversion / amplification circuit is too large, the input current will be too small on the contrary. By setting the photocurrent smaller than the input photocurrent, a certain amount of input current can be secured.

If a current mirror circuit is used as in claim 3, the above configuration can be realized by adding a relatively simple circuit to the conventional circuit.

According to claim 4, in addition to the effect of claim 1, the input current can be further reduced.

According to the fifth aspect, in the circuit configuration using the current mirror circuit, the current component to be deleted can be set smaller than the originally input photocurrent as in the case of the above-described second aspect. The amount of input current can be secured.

According to the circuit configuration of claim 6, the (first) current mirror circuit operates when the potential difference between both ends of the resistor becomes 0.7V. In this way, the potential difference becomes 0.7 V when the photocurrent value I _pd ON = 0.7 V / 1 KΩ = 700 μA or more when the resistance value is 1 KΩ. That is,
The circuit can operate when a large amount of light with a photocurrent of 700 μA or more is incident. Therefore, it is possible to avoid the problem that the photocurrent is further reduced even when the photocurrent is small.

By providing a delay circuit as described in claim 7 and delaying and adding a photocurrent (of opposite phase) that is smaller than the photocurrent to the original photocurrent, a current waveform with a sharp pulse edge is obtained. As a result, the recovery of the input stage transistor of the current-voltage converting / amplifying circuit from saturation is restricted, and the pulse blunting can be reduced.

A delay circuit according to a seventh aspect is the same as the eighth aspect.
It can be realized by a relatively simple circuit configuration using capacitors and resistors.

By providing the saturation prevention transistor as in the ninth and tenth aspects, it is possible to reduce the saturation of the input stage transistor of the current-voltage conversion amplifier circuit.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION The feature of the present invention is that in a device for inputting a photocurrent obtained by a light receiving element to a current-voltage conversion amplifier circuit, the obtained photocurrent is very large (that is, the amount of incident light is In the case of (very large), the photocurrent input to the current-voltage conversion amplifier circuit is reduced to prevent saturation in this circuit.

A first embodiment of the present invention will be described with reference to FIGS. Here, only the points different from the conventional circuit configurations shown in FIGS. 15 and 16 will be described. The difference from the circuits of FIGS. 15 and 16 is that the present invention firstly inserts a resistor R1 between the anode side of the light receiving element 100 and GND. Furthermore, the current mirror circuits 1 and 2 formed of PNP transistors are connected to the cathode side and the anode side of the light receiving element 100, respectively. The transistor Q100 in FIG. 15 is removed so that the operating range is not limited.

Here, the insertion of the resistor R1 is for expanding the operating range of the circuit, and the addition of the current mirror circuits 1 and 2 is for reducing the photocurrent. A large current (large amount of light) cannot be sufficiently dealt with only by expanding the operating range, so the photocurrent is further reduced. On the contrary, if the circuit configuration is such that only the reduction of the photocurrent is sufficient, it is possible to remove the resistor R1 only by adding the current mirror circuits 1 and 2.

The circuit operation of FIG. 1 will be specifically described below. First, the fact that the operating range of the circuit can be expanded by inserting the resistor R1 will be described with reference to FIG.
FIG. 3 shows a circuit configuration before the current mirror circuit is inserted. The circuit operation of FIG. 3 will be specifically described. The photocurrent I _pd generated in the light receiving element 100 is shunted and flows according to the resistance value of the resistor R1 and the input impedance of the current-voltage conversion amplifier circuit 3.

Assuming that the open loop gain of the amplifier when there is no feedback resistor Rf inside the current-voltage conversion amplifier circuit 3 is A, the input impedance Zi of the current-voltage conversion amplifier circuit 3 is Zi = Rf / (1 + A).・ It becomes (1). R1 takes a value close to Rf, and A is, for example, 10 ³
If it is sufficiently large, R1 >> Zi (2), and most of I _pd flows into the current-voltage conversion amplifier circuit 3. Therefore, the amplification operation is the same as in the conventional example, and the output voltage is Vha. = −I _pd × Rf (3) holds. Therefore, the operating range of Vha is the operating range of the current-voltage conversion amplifier circuit 3.

Next, the initial DC voltage of Vha is obtained. Assuming that the current amplification factor of the transistor Q101 is sufficiently large, the DC current Ir1 flowing through R1 is entirely flowing through Rf, and therefore the following formula is established.

Vha = Vin × (R1 + Rf) / R1 (4) When R1 = Rf, Vha = Vin × 2 = 2 × Vbe × 2 = 2.8V (5) I _pd is As a result, the voltage of Vha drops. The minimum collector voltage V _C of the transistor Q101 is about 1V.
Therefore, the minimum value of Vha is about 0.3V. Therefore, the operation ΔVha of Vha in the case of this example is ΔVha = 2.8V-0.3V = 2.5V (6), which is an improvement over the operating range of about 0.7V of the conventional example. .

FIG. 4 is a circuit diagram of another embodiment in which the resistor insertion location is changed. This circuit is an example in which the way of connecting the light receiving element 100 is different from that of FIG. 3, and one end of the light receiving element 100 is connected to the GND side. Also in this case, the operation is similar to that of FIG. 3, and the operation range of the current-voltage conversion amplifier circuit can be expanded by adding the resistor R1. However, as described above, even if the operation range is expanded in this way, it is not possible to sufficiently deal with a large current. For example, when the operating range is expanded to 2.5 V (ΔVha) (for simplicity, Rf = 25 kΩ), when the operating current range is ΔI, ΔI = ΔVha / Rf =
It becomes 2.5 / 25 kΩ = 100 μA, and cannot handle a current exceeding this.

Therefore, although the current mirror circuits 1 and 2 are provided as described above, this operation will be described below.

In the circuits of FIGS. 1 and 2, the light receiving element 1
A current Ipda having an opposite phase is created by using the current taken out from the cathode side of 00 and the current mirror circuit, and the current Ipda is added to the input of the current-voltage conversion amplifier circuit 3 to obtain the photocurrent Ipda.
Reduce minutes. Here, the current mirror circuits 1 and 2 are I
The setting is such that pd> Ipda. As a result, as apparent from FIG. 5, the current Iin input to the current-voltage conversion amplifier circuit 3 is the difference current between Ipd and Ipda. As a result, the saturation of the input transistor Q101, which has been a problem in the past, can be reduced.

[0052] and one specific example, the photocurrent limit can not cope When I _MAX in the insertion of the resistor R1 alone, the _{I MAX = ΔVha / Rf ··· (} 7).

Here, ΔVha = 2.5V, Rf = 20
When _{KΩ, I MAX = 2.5V / 20KΩ} = 125μA if I _pd: I _pda = 2: 1, then current I _in input to the amplifier _{I in = I pd -I pda =} I pd -1 / 2 · I _pd = 1/2 · I
_pd , and if I _pd = 200 μA, then I _in = 100
μA can be reduced.

In the above embodiment, the anode side of the light receiving element 100 is connected to the current-voltage conversion amplifier circuit 3, but as shown in FIG. 6, the cathode side of the light receiving element 100 is connected. You may comprise. In the case of this circuit, a current is taken out from the anode side of the light receiving element 100, a current having an opposite phase is generated, delayed, and added to the cathode side (input section to the current-voltage conversion amplifier circuit 3). Also in this example, the same operation and effect as in FIG. 1 can be obtained. In the following description of each embodiment and application example, the configuration shown in FIGS. 1 and 2 is representative, but the configuration shown in FIG. 6 can also be applied.

By the way, in the circuit configurations of FIGS. 1 and 2 (and FIG. 6), if the current mirror circuits 1 and 2 are constantly turned on, the photocurrent to the current-voltage conversion amplifier circuit 3 is obtained even when the light input is small. There is a possibility that the input is reduced and the light cannot be detected. Therefore, it is desirable that the current mirror circuit operates only when a large amount of light is input.

FIG. 7 is a circuit diagram of another embodiment which solves the above problems. This circuit is different from the circuit of FIG. 1 in that a resistor R is provided between the cathode side of the light receiving element 100 and the power supply VCC.
2 is added. As a result, the current mirror circuits 1 and 2 can be turned off when a minute photocurrent is input, and the input photocurrent Iin can be reduced only when a large amount of light is input.

Specifically, when the voltage on the cathode side of the light receiving element 100 is set to V _K and R2 = 1 KΩ is set, the value of Vcc-V _K is about 0. Must be 7V. Therefore, if the current at which the current mirror circuit 1 starts operating is IpdON, then IpdON = 0.7V / 1KΩ = 700 μA (8)

That is, in this example, when a large amount of light of 700 μA or more is generated, the circuit of the current mirror and the like of the present invention operates to reduce the input current.

As described above, by shifting the initial DC voltage of the current-voltage converting / amplifying circuit to expand the operation range and further reducing the input photocurrent by inserting the resistor R1,
Although the pulse dullness at the time of a large amount of light can be reduced, the pulse dullness at the time of a large amount of photocurrent can be further improved by FIGS. 8 to 10. 8 is a block circuit diagram according to another embodiment of the present invention, FIG. 9 is a specific circuit diagram of FIG. 8, and FIG. 10 is a more detailed circuit diagram thereof. The difference from the embodiment of FIG. 7 is that a resistor R3 and a capacitor C1 are provided between the current mirror circuits 1 and 2.
The point is that the delay circuit 4 consisting of is provided. The operation of this circuit will be described below.

First, qualitatively, as shown in the waveform diagram of FIG. 11, the opposite phase current extracted from the cathode side of the light receiving element 100 is delayed with respect to the photocurrent I _pd ,
When Ipda is created and added to the input of the current-voltage conversion amplifier circuit 3, the current waveform of I _in of FIG. 10 is obtained, and the current waveform of which the edge of the pulse is sharper than the original current waveform of I _pd is obtained. As a result, the input transistor of the current-voltage conversion amplifier circuit 3 recovers quickly from saturation, and Vha of the current-voltage conversion amplifier circuit 3 and the output of the 2nd amplifier V2
Each nd can reduce the pulse bluntness and thus faithfully reproduce the pulse width at the comparator output V _O.

Next, a specific circuit configuration will be described.

In FIG. 10, the photocurrent is I _pd and the resistance R2 is
Ir ₂ the current flowing through the, the current input to the current mirror circuit 1 I _pdi, the output current of the current mirror circuit I
_pdo , the current input to the current mirror circuit 2 is Ir ₃ ,
The output current of the current mirror circuit 2 is I _pda , and the current input to the current-voltage conversion amplifier circuit 3 is I _in . First, for simplicity, I _pdi = I _pd (9) This has almost no influence on the operation description.

If the output: input ratio of the current mirror circuit is set to 1/2, then I _pdo = 1/2 × I _pdi = 1/2 × I _pd (10) antiphase current I _pda delayed by the delay circuit 4 constructed from C1 and R3 Prefecture, when the rise and after the current waveform of the pulse and _{I pda r, I pda r =} Ir3 = I pdo-p × {1- exp (-t / C1 / R3)} (11) where I _pdo-p is the peak value of I _pdo .

The current waveform after the fall of the pulse is I
When _{pda f,} the _{I pda f = Ir3 = I pdo} -p × exp (-t / C1 / R3) ··· (12).

From the equations (10), (11) and (12), the current I _in input to the current-voltage conversion amplifier circuit is obtained. Similarly to the above, the current waveform after the pulse rise is I _{pda r} ,
_Let I _{pda f} be the current waveform after the fall of the pulse, and
When the peak value of _pd and _{I pd-p, I in r} = I pd-p -I pda r = I pd-p -I pd-p / 2 × {1-exp (-t / C1 / R3)} _{= I pd-p / 2 +} I pd-p / 2 × exp (-t / C1 / R3) ··· (13) I in f = I pd - I pda f = I pd - I pd-p / 2 × exp (-t / C1 / R3) ... (14). In the equation (7), since I _pd = 0 after the rising _edge of the pulse, I _{in f} = −I _pd-p / 2 × exp (−t / C1 / R3) (15) FIG. 12 shows equations (10) to (15) with detailed current waveforms. FIGS. 12A and 12B are a waveform diagram before current value combination and a waveform diagram after (currently input by) current value combination, respectively. In FIG. 12, the rise time and the fall time of the photocurrent pulse are neglected and shown as being very short. As can be seen from FIG. 12, the current I _in input to the current-voltage conversion / amplification circuit has a current waveform with a sharp edge, and when the current waveform falls, the base terminal of the saturated input transistor Q101 accumulates. It forcibly pulls out the charge and helps recover from saturation, increasing the recovery speed.

FIGS. 13 and 14 show an example in which the saturation prevention circuit 5 is added to FIGS. 8 to 10 to further reduce the saturation of the input stage transistor of the current-voltage conversion amplifier circuit 3. In FIG. 13, the resistance R is on the anode side of the light receiving element 100.
Connected to the input of the current-voltage conversion amplifier circuit 3 via 4,
A diode Q1 is connected between the anode of the light receiving element 100 and the collector of the input stage transistor Q1 of the current-voltage conversion amplifier circuit 3.

In this circuit configuration, when I _pd increases, the anode terminal voltage V _A of the light receiving element 100 rises due to the voltage drop across the resistor R4, and the transistor Q101
When the collector voltage V _C of the diode decreases, I _pd becomes diode Q1.
Flowing into the collector of the transistor Q101, the saturation of the transistor Q101 is reduced. The shallower the saturation of the transistor Q101, the greater the effect of accelerating the recovery from the saturation as shown in FIG.

FIG. 14 is an example in which a saturation reducing means different from that of FIG. 13 is added, and the anode of the light receiving element 100, that is,
The PNP transistor Q is connected to the input of the current-voltage conversion amplifier circuit 3.
2 is connected, the collector of the transistor Q2 is connected to GND, and the base terminal is connected to the output Vha of the current-voltage conversion amplifier circuit 3.

In this circuit configuration, the photocurrent I _pd increases, the voltage of Vha decreases, and the value of V _in -Vha is about 0.
When the voltage exceeds 7V, the transistor Q2 operates and I _pd flows into the emitter of Q2 and exits from GND. As a result, the input transistor Q10 of the current-voltage conversion amplifier circuit 3 is
The saturation of 1 is reduced.

[0070]

As described above, according to the present invention,
The operating range of the amplification circuit itself of the light receiving and amplification device can be greatly expanded, and the input current to the amplification circuit at the time of a large amount of light can be reduced. Further, even if the light receiving and amplifying circuit is saturated, the depth of the saturation can be reduced, and the recovery from the saturation can be speeded up. As a result, even when a large amount of light is input, the pulse generated by the optical signal can be faithfully reproduced, and the photocurrent operating range of the light receiving and amplifying device itself can be greatly expanded.

Moreover, since it can be realized by adding a relatively simple circuit, integration and circuit design are easy.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a photoreceiver / amplifier according to an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of FIG.

FIG. 3 is a circuit diagram for explaining derivation of the circuit in FIG.

FIG. 4 is another circuit diagram for explaining the derivation of the circuit of FIG.

5A to 5C are waveform diagrams of various parts of the circuit of FIG.

FIG. 6 is a block circuit diagram of a photoreceiver / amplifier according to another embodiment of the present invention.

FIG. 7 is a circuit diagram of a photoreceiver / amplifier according to still another embodiment of the present invention.

FIG. 8 is a block circuit diagram of a photoreceiver / amplifier according to still another embodiment of the present invention.

9 is a specific circuit diagram of FIG.

FIG. 10 is a detailed circuit diagram of FIG. 9.

11A to 11F are waveform diagrams of respective parts of the circuit of FIG.

12A and 12B are waveform charts for explaining the effect of the circuit of FIG.

FIG. 13 is a circuit diagram of a photoreceiver / amplifier according to still another embodiment of the present invention.

FIG. 14 is a circuit diagram of a photoreceiver / amplifier according to still another embodiment of the present invention.

FIG. 15 is a block circuit diagram of a light receiving and amplifying device according to a conventional example.

16 is a specific circuit diagram of FIG.

17 (a) to (d) are waveform diagrams of respective portions of the circuit of FIG.

FIG. 18 is a waveform diagram for explaining problems of the circuit of FIG.

19 (a) and 19 (b) are waveform diagrams of signal transmission by the IrDA system, respectively.

[Explanation of symbols]

 1 1st current mirror circuit 2 2nd current mirror circuit 3 current-voltage conversion amplifier circuit 4 delay circuit 5 saturation prevention circuit 100 light receiving element R1 shunt resistor R2 switching resistor Q2 saturation prevention transistor

Claims (10)

[Claims] 1. A light-receiving element and a current-voltage conversion amplifier circuit for amplifying a photocurrent generated in the light-receiving element, wherein the photocurrent of the light-receiving element is the current voltage from either one of an anode or a cathode of the light-receiving element. In the light-receiving / amplifying circuit input to the conversion / amplifying circuit, a current is also taken out from the other end of the light-receiving element, and the amount of the current is reduced from the photocurrent input to the current / voltage conversion / amplifying circuit from one end of the light-receiving element. A photoreceiver / amplifier circuit characterized by the above. 2. The photoreceiver / amplifier circuit according to claim 1, wherein a current component taken out from the other end of the photoreceiver element is smaller than a photocurrent inputted from the one end of the photoreceiver element to the current-voltage conversion amplifier circuit. A photoreceiver / amplifier circuit characterized by being configured to reduce the number. 3. The light receiving / amplifying circuit according to claim 1, wherein the other end of the light receiving element different from the input end to the current / voltage converting / amplifying circuit has an input of a first current mirror circuit formed of a transistor. The second current mirror circuit is connected to the output section of the first current mirror circuit, and the input section of the second current mirror circuit composed of a transistor having a polarity opposite to that of the first current mirror circuit is connected to the second current mirror circuit. A light-receiving / amplifying circuit, wherein an output portion of the circuit is connected to an input terminal of the light-receiving element to a current / voltage converting / amplifying circuit. 4. The light-receiving / amplifying circuit according to claim 1, wherein a branch connecting a shunt resistor is provided at an input end of the light-receiving element to the current-voltage converting / amplifying circuit.
A light receiving / amplifying circuit for dividing a photocurrent to the current / voltage converting / amplifying circuit according to a ratio of a resistance value of the shunt resistor and an impedance of the current / voltage converting / amplifying circuit. 5. The photoreceiver / amplifier circuit according to claim 3, wherein the current output value of at least the first current mirror circuit of the first and second current mirror circuits is set smaller than the current input value. A photoreceiver / amplifier circuit characterized by the following. 6. The photoreceiver / amplifier circuit according to claim 3, wherein a resistor is provided between the other end of the photoreceiver element to which the first current mirror circuit is connected and a power supply or GND, and the current voltage is increased. The photocurrent input to the conversion amplifier circuit is
A light receiving and amplifying circuit, characterized in that the first and second current mirror circuits are operated only when a current value exceeds a predetermined value. 7. The photoreceiver / amplifier circuit according to claim 3, wherein an output portion of the first current mirror circuit and the second
A delay circuit for delaying the phase of the current extracted from the other end of the light receiving element from the input part of the current mirror circuit than the phase of the current input from the one end of the light receiving element to the current-voltage conversion amplifier circuit. A photoreceiver / amplifier circuit characterized by being provided. 8. The photoreceiver / amplifier circuit according to claim 7, wherein the delay circuit includes a capacitor and a resistor whose one ends are commonly connected, and the connection point of the delay circuit is an output portion of the first current mirror circuit. The resistor is inserted between the output part of the first current mirror circuit and the input part of the second current mirror circuit, and the other end of the capacitor is connected to GND or a power supply. A photoreceiver / amplifier circuit characterized by the above. 9. The light receiving and amplifying circuit according to claim 3,
Between the light receiving element and the current-voltage conversion amplification circuit, a saturation prevention circuit for preventing saturation of the input stage transistor provided in the input section of the current-voltage conversion amplification circuit is provided, and the saturation prevention circuit is One end is composed of a saturation prevention resistor commonly connected and a saturation prevention transistor whose base and emitter are short-circuited, the connection point of the saturation prevention circuit is connected to the light receiving element, and the other end of the saturation prevention resistor is A light receiving and amplifying circuit, which is connected to an input part of the current-voltage converting and amplifying circuit, and the other end of the saturation prevention transistor is connected to a collector of the transistor of the input stage. 10. The photoreceiver / amplifier circuit according to claim 3, wherein a saturation prevention transistor for preventing saturation of the input-stage transistor is provided in the input-stage transistor provided in the input section of the current-voltage conversion amplifier circuit. A light-receiving / amplifying circuit, wherein the saturation preventing transistor has an emitter and a base connected to an input and an output of the current-voltage converting / amplifying circuit, respectively, and a collector connected to GND or a power supply.