JPH0817336B2 - Signal receiving circuit and optical pulse receiving circuit using the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal receiving circuit for reproducing an output signal without distortion regardless of amplitude fluctuation of an input signal voltage, and an optical pulse receiving circuit using the signal receiving circuit.

[Conventional technology]

As a signal receiving circuit of this type, a configuration shown in FIG. 8 has been conventionally known. In the figure, 1 is an input terminal to which an input signal voltage is input, and the input terminal 1 is input to this input terminal 1. Input signal voltage V _IN passes through buffer 2 and voltage comparator 3
And the threshold voltage V _T from the threshold voltage generating circuit 4 is input to the comparison reference voltage terminal of the voltage comparator 3. Here, the threshold voltage generating circuit 4
The threshold voltage V _T is output by dividing the power supply voltage + V with the resistor 5 and the variable resistor 6.

Then, the voltage comparator 3 compares the input signal voltage V _IN with the threshold voltage V _T and outputs the output signal voltage obtained by reproducing the input signal voltage.

By the way, generally, when a pulse signal is transmitted to a signal receiving circuit via a transmission medium, the original rectangular signal wave is dull and attenuated by the transmission medium. Therefore, the input signal voltage V _IN received by the signal receiving circuit greatly changes depending on the distance and the characteristics of the transmission medium, and the level changes like the input signal voltage V _IN1 V _IN2 shown in FIG. 9A.

In this way, when the input signal voltage input to the input terminal 1 of the signal receiving circuit fluctuates, the threshold voltage V _T generated by the threshold voltage generating circuit 4 becomes a constant value after it is set in the initial state. When the output signal voltage V _OUT output from the voltage comparator 3 is a high level input signal voltage V _IN1 , as shown in FIG. 9 (b), the pulse width T of which the pulse width in the ON state is wide T _{When the} input signal voltage V _IN2 is _W1 and the level is low, as shown in FIG. 9 (c), the pulse width of the ON state is the pulse width T _W1.
A narrower pulse width T _W2 is obtained.

As a result, due to the level fluctuation of the input signal voltage, | T
There was a problem that pulse width distortion (variation) of _W1- T _W2 |

In order to solve this problem, a signal receiving circuit shown in FIG. 10 has been conventionally proposed.

This signal receiving circuit supplies the output signal of the buffer 2 to the automatic threshold control circuit 7 to change the threshold voltage V _{T according} to the input signal voltage. This automatic threshold control circuit 7
Supplies the output voltage of the buffer 2 to the capacitor 9 via the diode 8 and holds the peak of the voltage obtained by subtracting the voltage drop of the diode 8 at this capacitor 9, and the held voltage is set to ₁ by the resistors R ₁ and R ₂ . Threshold voltage V divided by 2
_T, and this is supplied to the comparison reference voltage input terminal of the voltage comparator 3.

[Problems to be Solved by the Invention]

However, in the conventional signal receiving circuit shown in FIG. 10, the threshold voltage V _T is set according to the input signal voltage by setting the threshold voltage V _T to a voltage that is half the peak voltage of the input signal voltage. Since the pulse width distortion of the output signal voltage due to the fluctuation of the input signal voltage can be reduced because it is controlled automatically, the voltage drop of the diode is large and it is applied to, for example, an optical pulse receiving circuit that handles a minute voltage. There was an unsolved problem that the dynamic range could not be made so large as not being possible.

Further, when there is no signal, there is an unsolved problem that the compared voltage of the voltage comparator 3 becomes equal to the comparison reference voltage, and malfunction occurs due to the influence of noise or the like.

Therefore, the present invention focuses on the unsolved problem of the above-described conventional example, and can be applied to a signal receiving circuit that handles a minute voltage, and malfunctions due to noise or the like may occur when there is no signal. An object of the present invention is to provide a non-signal receiving circuit and an optical pulse receiving circuit using the same.

[Means for solving the problem]

In order to achieve the above-mentioned object, the signal receiving circuit according to claim (1) is an automatic threshold control in which a signal obtained by superimposing a minute voltage on a divided value of an input signal voltage is supplied to a peak hold circuit as a threshold voltage. A circuit and a voltage comparator for comparing the threshold voltage of the automatic threshold control circuit with the input signal voltage are provided.

An optical pulse receiving circuit according to claim (2) is an automatic threshold control circuit that divides a voltage obtained by peak-holding an input signal voltage by a peak-hold circuit to obtain a threshold voltage, a threshold voltage of the threshold control circuit, and the threshold voltage. A voltage comparator that compares the input signal voltage with a cutoff unit that compares the peak hold voltage of the peak hold circuit with a minute voltage and shuts off the output of the voltage comparator when the peak hold voltage is less than the minute voltage. It is characterized by having and.

Furthermore, the optical pulse receiving circuit according to claim (3) includes a photoelectric conversion element that converts an optical signal into a current signal, and a current-voltage converter that converts a current signal output from the photoelectric conversion element into a voltage signal. An optical pulse receiving circuit comprising an amplifier for amplifying the output voltage of the current-voltage converter and a signal receiving circuit for comparing the output voltage of the amplifier with a threshold voltage,
The signal receiving circuit, an automatic threshold control circuit that supplies a signal obtained by superimposing a minute voltage on the divided voltage value of the output voltage of the amplifier to a peak hold circuit to set the threshold voltage, and a threshold voltage of the automatic threshold control circuit. And a voltage comparator for comparing the output voltage of the amplifier.

Furthermore, the optical pulse receiving circuit according to claim (4) is a photoelectric conversion element for converting an optical signal into a current signal, and a current-voltage converter for converting a current signal output from the photoelectric conversion element into a voltage signal. And an amplifier that amplifies the output voltage of the current-voltage converter, and a signal receiving circuit that compares the output voltage of the amplifier with a threshold voltage, wherein the signal receiving circuit includes the current- An automatic threshold control circuit that amplifies a signal obtained by superimposing a minute voltage on a divided voltage value of an output voltage of a voltage converter and supplies it to a peak hold circuit as a threshold voltage, a threshold voltage of the automatic threshold control circuit, and the amplifier. And a voltage comparator for comparing the output voltage of the.

Still further, the optical pulse receiving circuit according to claim (5) is a photoelectric conversion element for converting an optical signal into a current signal, and a current-voltage converter for converting a current signal output from the photoelectric conversion element into a voltage signal. And an amplifier for amplifying the output voltage of the current-voltage converter, and a signal receiving circuit for comparing the output voltage of the amplifier with a threshold voltage, wherein the signal receiving circuit is An automatic threshold control circuit that sets a voltage obtained by peak-holding the amplified output as a threshold voltage as a divided voltage, a voltage comparator that compares the threshold voltage of the automatic threshold control circuit with the output voltage of the amplifier, and a peak of the peak hold circuit. A holding means for comparing the hold voltage with a minute voltage and cutting off the output of the voltage comparator when the peak hold voltage is less than the minute voltage. .

[Action]

In the signal receiving circuit according to claim (1), since the automatic threshold control circuit supplies a voltage obtained by superimposing a minute voltage to the divided value of the input signal voltage to the peak hold circuit and peak-holds the threshold voltage. When the level fluctuation of the input signal voltage occurs, the threshold voltage is controlled according to the level change so that it becomes a divided voltage value of the voltage amplitude to be compared. It is possible to prevent the resulting pulse width distortion from occurring, and
By superimposing a small voltage, even when there is no signal,
It is possible to generate a threshold voltage according to a minute voltage, remove the influence of noise or the like, and eliminate malfunction.

Further, in the signal receiving circuit according to claim (2),
The input signal voltage is peak-held by the peak-hold circuit, and the held voltage is divided into the threshold voltage, so pulse width distortion caused by the level fluctuation of the input signal voltage is prevented, and the peak-hold voltage is cut by the cutoff means. Since the output of the voltage comparator is cut off when the former is lower than the latter, the influence of noise and the like at the time of no signal can be removed and the subsequent operation can be eliminated.

Further, in the optical pulse receiving circuit according to claim (3), an optical signal is converted into a current signal by the photoelectric conversion element, this is converted into a voltage signal by the current-voltage conversion circuit, and the voltage signal is amplified by the amplifier. Since the signal is supplied to the same signal receiving circuit as in claim (1) to generate the threshold voltage, it is possible to prevent the fluctuation of the output pulse width due to the change of the light intensity of the optical signal, and Malfunctions can be eliminated by removing the influence of noise and the like at the time of signalling.

Furthermore, in the optical pulse receiving circuit according to claim (4), since the voltage signal converted into the voltage signal by the current-voltage conversion circuit is supplied to the automatic threshold control circuit, it is amplified from the above-mentioned claim (3). Since the only difference is whether the voltage is supplied to the automatic threshold control circuit or amplified in the automatic threshold control circuit, the same operation as described above can be obtained.

Furthermore, in the optical pulse receiving circuit according to claim (5), an optical signal is converted into a current signal by a photoelectric conversion element,
This is converted into a voltage signal by the current-voltage conversion circuit, and the voltage signal amplified by the amplifier is supplied to the same signal receiving circuit as in claim (2) to generate the threshold voltage. It is possible to prevent the fluctuation of the output pulse width due to the change of the light intensity of the optical signal, and it is possible to eliminate the influence of noise and the like when there is no signal to eliminate the malfunction.

〔Example〕

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

FIG. 1 is a block diagram showing a first embodiment of the present invention.

In the figure, 1 is a pulsed input signal voltage via the transmission medium.
The input signal voltage V _{IN which} is an input terminal to which V _IN is supplied and which is input to the input terminal 1 is input to the compared voltage terminal of the voltage comparator 3 via the buffer 2.

On the other hand, the input signal voltage V output from the buffer 2
_IN is supplied to the voltage dividing circuit 11 in the automatic threshold control circuit A.
Voltage divider circuit 11 is constituted by resistors R ₁ and R _2, resistors R ₁ and R ₂ of the degree of micro-input offset compared to the input signal voltage V _IN can substantially negligible from the reference voltage generator 12 to the connection point Voltage V
_{The OS} is supplied, and this minute input offset voltage V _OS is superimposed on the divided voltage value of the input signal voltage V _IN .

Then, the superimposed signal voltage output from the connection point of the resistors R ₁ and R ₂ of the voltage dividing circuit 11 is input to the peak hold circuit 14 via the buffer 13.

In this peak hold circuit 14, the output signal of the buffer 13 is input to the non-inverting input side, the diode 15 and the holding capacitor 16 are connected in series between the output side and the ground, and the resistor 17 is connected in parallel with the capacitor 16. It has a connected non-inverting type operational amplifier 18, the connection point of the capacitor 16 and the resistor 17 is connected to the inverting input side of the operational amplifier 18,
The peak hold voltage output from the connection point of the capacitor 16 and the resistor 17 is input to the comparison reference voltage terminal of the voltage comparator 3 as the threshold voltage V _T.

Next, the operation of the first embodiment will be described. Now, assuming that the input signal voltage V _IN with and level variations cause rounding to the input terminal 1 via the transmission medium is input, the input signal voltage V _IN, the voltage comparator 3 via the buffer 2
Since the voltage is input to the compared voltage terminal of and is also supplied to the voltage dividing circuit 11, the voltage dividing circuit 11 divides the voltage into 1 / N. On the other hand, the minute input offset voltage V _OS from the reference voltage generator 12 is supplied to the voltage dividing circuit 11, and this minute input offset voltage V _OS is set to the divided voltage value V _IN / N of the input signal voltage V _IN. Since it is superimposed, the output voltage V _D of the voltage dividing circuit 11 becomes V _D = V _IN / N + V _OS ≈V _IN / N (1), and this output voltage is supplied to the peak hold circuit 14 via the buffer 13. This peak hold circuit
At 14, the peak value is held for a holding time according to the time constant determined by the capacitor 16 and the resistor 17, and this is held at the threshold voltage V _T.
Is supplied to the comparison reference voltage terminal of the voltage comparator 3. Therefore, the input signal voltage V _IN from the voltage comparator 3 becomes equal to the threshold voltage V
When the voltage exceeds _T , the output voltage V _OUT that becomes the logical value “1” is output.

By the way, as described above, since the input signal voltage input to the input terminal 1 via the transmission medium is blunted and accompanied by level fluctuation, for example, as shown by the solid line in FIG. When the input signal voltage V _IN1 having a large level is input to the input terminal 1, the output voltage V _D output from the voltage dividing circuit 11 has a large value, which is the buffer 13
Since it is supplied to the peak hold circuit 14 via the peak hold circuit 14, the peak value held in the peak hold circuit 14 is as shown by the solid line in FIG. 2 (a) according to the large level of the input signal voltage V _IN1 . The peak value of the input signal voltage V _IN1 becomes a value obtained by substituting in the equation (1), and this value is input to the comparison reference voltage terminal of the voltage comparator 3 as the threshold voltage V _T , so the output voltage V of this voltage comparator 3 _As shown in FIG. 2B, _OUT1 maintains the logical value "0" until the input signal voltage V _IN1 exceeds the threshold voltage V _T1 and exceeds the threshold voltage V _T1 at time t. _{When the} value is ₁ , the logic value “1” is refuted, and thereafter, at the time point t ₂ when the voltage becomes less than the threshold voltage V _T1 , it is inverted again to the logic value “0”.

On the other hand, when a small level input signal voltage V _IN2 is input to the input terminal 1 as shown by the broken line in FIG. 2 (a), the level of the output voltage V _D of the voltage dividing circuit 11 is also reduced accordingly. Therefore, the threshold voltage V _T2 output from the peak hold circuit 14 also has a small value as shown by the broken line in FIG. Therefore, the output voltage V _OUT2 of the voltage comparator 3 is
As shown in FIG. 7C, the large level input signal voltage V
Similar to _IN1, it is inverted to the logical value “1” at time t ₁ and is inverted to the logical value “0” at time t ₂ , and the same pulse width T _W regardless of the level fluctuation of the input signal voltage V _IN. The pulse output voltage can be obtained, and the pulse width distortion can be reliably prevented.

Further, when the input signal voltage V _IN is zero and there is no signal, the voltage dividing circuit 11 outputs a minute voltage of only the minute input offset voltage V _OS , which is the peak hold circuit.
Since the threshold voltage V _T is the peak hold at 14, the threshold voltage V _T is as shown in FIG. 3 (a), becomes a small input offset voltage V _OS minute high value, this comparison reference voltage comparator 3 Since it is input to the voltage terminal, the temporary input signal voltage
Even when low level noise is mixed in V _IN ,
The output voltage V _OUT of the voltage comparator 3 maintains the logic value "0" as shown in FIG. 3 (b), causing a malfunction that the output voltage V _OUT of the voltage comparator 3 inverts the influence of noise or the like There is no.

Next, a second embodiment of the present invention will be described with reference to FIG.

This second embodiment shows an embodiment in which the signal receiving circuit of the first embodiment described above is applied to an optical pulse receiving circuit.

That is, as shown in FIG. 4, the optical pulse transmitted through the optical transmission medium 20 such as an optical fiber has a positive power supply terminal +
The current is controlled according to the light intensity of the optical pulse that is input to the photodiode 21 as a photoelectric conversion element connected between V and ground, and this current is connected in series with the photodiode 21. The converted voltage conversion resistor 22 converts the voltage signal.

This voltage signal is amplified by the non-inverting amplifier circuit 24 composed of the operational amplifier 23 and the resistors R ₁₁ and R ₁₂ , and input to the signal receiving circuit 25.

The signal receiving circuit 25 includes a voltage comparator 26 to which the amplified output V _IN from the non-inverting amplifier circuit 24 is input to the compared voltage terminal and an automatic threshold control circuit A, and the automatic threshold control circuit A is A voltage divider circuit 27 having resistors R ₁₃ and R ₁₄ to which the amplified output V _IN of the inverting amplifier circuit 24 is supplied, an operational amplifier 28 to which the output voltage of the voltage divider circuit 27 is input, a resistor R ₁₅ and a resistor R _15.
A non-inverting amplifier circuit 29 composed of ₁₆ and a peak hold circuit 30 which inputs the amplified output of the non-inverting amplifier circuit 29 and outputs the peak hold value as a threshold voltage to the comparison reference voltage terminal of the voltage comparator 26. I have it.

Here, on the inverting input side of the non-inverting amplifier circuit 29, a reference voltage generator 31 in which a variable resistor VR ₁ is connected between a positive power source and a negative power source is used.
The minute input offset voltage V _{OS of} is input. The peak hold circuit 30 includes an operational amplifier 32, a diode, as in the peak hold circuit 14 of the first embodiment.
33, a capacitor 34 and a resistor 35.

Next, the operation of the second embodiment will be described. Optical transmission medium
The light pulse from 20 is converted into a voltage by the photodiode 21 and the resistor 22, amplified by the non-inverting amplifier circuit 24,
The amplified output V _IN is input to the compared voltage terminal of the voltage comparator 25, and also input to the voltage dividing circuit 26 to be divided into 1 / M. Therefore, the output voltage V _D of the voltage dividing circuit 27 is V _IN × (1 /
M).

By inputting this divided voltage to the non-inverting amplifier circuit 29, the non-inverting amplifier circuit 29 multiplies it by M / K and superimposes the minute input offset voltage V _OS input to its inverting input side. Therefore, the output voltage V of the non-inverting amplifier circuit 29
_A becomes V _A = {V _IN / M)} × (M / K) + V _OS = (V _IN / K) + V _OS ≈V _IN / K (2).

The output voltage V _A expressed by the equation (2) is the above-mentioned first voltage
Since the output voltage V _{D of the} voltage dividing circuit 11 input to the peak hold circuit 14 in the embodiment has a value equal to that of the first embodiment, it is possible to obtain the same effect as that of the first embodiment. It is possible to obtain a reception output that does not cause pulse width distortion regardless of the change in the light intensity of
No adjustment is required for variations in the length of the optical transmission medium 20, variations in coupling loss of the optical connector, variations in emission power of the optical transmitter, deterioration, and the like, and the threshold voltage is a non-inverting amplifier circuit 29 when there is no signal. Since it is fixed to the offset voltage of 1, it is possible to discriminate no signal and eliminate malfunctions due to noise or the like.

Next, a third embodiment of the present invention will be described with reference to FIG.

In the third embodiment, a transimpedance amplifier 41 is applied instead of the resistor 22 as the current-voltage converting means in the second embodiment, and the same reference numerals are given to the portions corresponding to those in FIG. The detailed description thereof will be omitted.

That is, as shown in FIG. 5, in the configuration of FIG. 4, the resistor 22 is omitted and the anode of the photodiode 21 constitutes the transimpedance amplifier 41, and the resistor R ₄₁ is interposed between the inverting input side and the output side. The output voltage of the transimpedance amplifier 41 connected to the inverting input side of the operational amplifier 42 is inverted and amplified by the inverting amplifier circuit 44 composed of the operational amplifier 43 and the resistors R ₄₂ and R ₄₃ , and the voltage comparator 25
Of the voltage to be compared and is supplied to the voltage dividing circuit 45 of the automatic threshold control circuit A.

The voltage dividing circuit 45 is composed of resistors R ₄₄ and R ₄₅ , and this divided voltage V _D is supplied to an inverting amplifier circuit 47 composed of an operational amplifier 46 and resistors R _{46 to} R ₄₈ . The output voltage V _A is input to the peak hold circuit 30, and the inverting amplifier circuit
The minute input offset voltage V _OS from the reference voltage generator 31 is input to the non-inverting input side of 47.

According to the third embodiment, the optical pulse from the optical transmission medium 20 is converted into a voltage whose polarity is inverted by the photodiode 21 and the transimpedance amplifier 41, and further inverted and amplified by N times in the inverting amplifier circuit 44. Amplified output V
_IN is input to the compared voltage terminal of the voltage comparator 25.

On the other hand, the output voltage (= V _IN / N) of the transimpedance amplifier 41 is divided into 1 / M by the voltage dividing circuit 45, and the divided voltage V _D is V _D = V _IN / N ・ (1 / M) Is supplied to the inverting input side of the operational amplifier 46 of the inverting amplifier circuit 47. This inverting amplifier circuit 47 multiplies by N · M / K and superimposes the minute input offset voltage V _OS input to its inverting input side. Therefore, the output voltage V _A of the inverting amplifier circuit 47 is V _A = {V _IN / (N · M)} × (N · M / K) + V _OS = (V _IN / K) + V _OS ≈V _IN / K ... (3), which is input to the peak hold circuit 30, and the peak hold value is input to the comparison reference voltage terminal of the voltage comparator 25 as the threshold voltage V _T.

Therefore, the output voltage V _{A of the} inverting amplifier circuit 47, which is input to the peak hold circuit 30, is represented by the above equation (3), which is exactly the same as the equation (2) in the second embodiment. It is possible to obtain the same effect as that of the second embodiment described above.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

The fourth embodiment shows a modification of the signal receiving circuit of the first embodiment, and the portions corresponding to those in FIG. 1 are designated by the same reference numerals and the detailed description thereof will be omitted.

That is, as shown in FIG. 6, in the configuration of FIG. 1, the voltage dividing circuit 11 and the reference voltage generator 12 are omitted, and the output voltage of the buffer 2 is the compared voltage of the voltage comparator 3'with the strobe terminal. The peak hold circuit 14 of the automatic threshold control circuit A is supplied directly to the terminal and the peak hold voltage V _P of the peak hold circuit 14 is supplied to the voltage dividing circuit 53 composed of the resistors 51 and 52. The divided voltage of the voltage dividing circuit 53 is used as the threshold voltage V _T , and the voltage comparator with strobe terminal 3 '
It is supplied to the comparison voltage terminal of and the peak hold circuit 14
The peak hold voltage V _P of is input to the other end of the comparator 55, which receives the minute input offset voltage V _OS from the reference voltage generator 54 at one end, and is output from this comparator 55 when V _P <V _OS. The enable signal is inputted to the strobe terminal 3a of the voltage comparator 3 '.

According to the fourth embodiment, the peak hold voltage V _P obtained by peak-holding the input signal voltage in the peak hold circuit 14
Is divided by the voltage dividing circuit 53 to be supplied to the comparison voltage terminal of the voltage comparator 3'as the threshold voltage V _T , and the dynamic range is compared with the case where the voltage drop due to the diode is divided as in the conventional example. Can be widened, and when the peak hold value V _P of the input signal voltage and the minute input offset value V _OS are compared, and V _P <V _OS , the strobe terminal 3a of the voltage comparator 3'can be enabled. Since a signal is input, when the input signal voltage is zero, the voltage comparator 3'is always in the non-operating state and in the non-signal state.
It is possible to obtain the same effect as that of the first embodiment described above.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

The fifth embodiment is an application of the signal receiving circuit of the fourth embodiment to an optical pulse receiving circuit.

That is, as shown in FIG. 7, the optical pulse transmitted through the optical transmission medium 21 is input to the photodiode 22 as a photoelectric conversion element, and the anode of the photodiode 22 is connected to the current-voltage converter 61. The output voltage of the current-voltage converter 61 is amplified by the amplifier 62, and the amplified output is supplied to the signal receiving circuit 63 having the same configuration as that of FIG.

According to the fifth embodiment, the optical pulse transmitted through the optical transmission medium 21 is received by the photodiode 22, and the current output from the photodiode 22 is converted into a voltage value by the current-voltage converter 61. The converted signal is amplified by the amplifier 62 and supplied to the signal receiving circuit 63.
At 63, it is possible to obtain a reception output that does not cause pulse width distortion regardless of the change in the light intensity of the optical pulse, and when the optical pulse is non-signal, the peak hold circuit 14 of the signal receiving circuit 63.
By comparing the peak hold value V _P of the input voltage with the minute input offset voltage V _OS and supplying the enable signal to the strobe terminal 3a of the voltage comparator 3 ', the voltage comparator 3'is brought into a non-differential state and its output is output. As a no-signal state, the influence of noise or the like can be eliminated.

In the fourth and fifth embodiments, the case where the voltage comparator with strobe terminal 3'is applied as the voltage comparator has been described, but the present invention is not limited to this, and a normal voltage comparator is applied. Then, a gate circuit may be provided on the output side of this voltage comparator, and the comparison output of the comparator 55 may be supplied to this gate circuit to close the gate circuit when there is no signal.

〔The invention's effect〕

As described above, according to the signal receiving device of the first aspect, the signal voltage in which the minute voltage is superimposed on the divided value of the input signal voltage is peak-held by the automatic threshold control circuit, and this peak-hold value is Since the threshold voltage is set and this threshold voltage is compared with the input signal voltage by the voltage comparator,
It is possible to obtain a received signal with no pulse width distortion regardless of the level fluctuation of the input signal voltage, and the threshold voltage becomes a high level by a minute voltage when there is no input signal voltage and there is no influence of noise. It is possible to obtain the effect of reliably eliminating malfunction.

According to the signal receiving circuit of claim (2), the input signal voltage is peak-held by the peak-holding circuit,
This is divided into a threshold voltage, and the peak hold voltage is compared with the minute voltage. When the peak hold voltage is lower than the minute voltage, it is judged that there is no signal, and the output of the voltage comparator is cut off. Therefore, it is possible to obtain the same effect as that of claim (1).

Further, according to the optical pulse receiving circuit of claim (3), the optical signal is converted into a current value by the photoelectric conversion element, and the current value is converted into a voltage value by the current-voltage conversion circuit, and the value is amplified and the voltage is compared. By knowing the received signal without pulse width distortion regardless of the fluctuation of the light intensity of the optical pulse input to the photoelectric conversion element, by inputting it to the compared voltage terminal of the device and supplying it to the automatic threshold control circuit described above. As well as
Since the threshold voltage becomes a high level by a minute voltage when there is no signal in the absence of an optical pulse, it is possible to reliably eliminate the malfunction caused by the influence of noise or the like.

Furthermore, according to the optical pulse receiving circuit of claim (4), the value converted into the voltage value by the current-voltage conversion circuit is supplied to the automatic threshold control circuit, and the value is amplified and thresholded in the automatic threshold control circuit. Since the voltage is obtained, it is possible to obtain the same effect as the above-mentioned claim (3).

Still further, according to the optical pulse receiving circuit of claim (5), the value converted into the voltage value by the current-voltage converting circuit is amplified by the amplifier and supplied to the signal receiving circuit of claim (2). Therefore, it is possible to obtain the same operational effects as the above claims (3) and (4).

[Brief description of drawings]

FIG. 1 is a block diagram of a signal receiving circuit showing a first embodiment of the present invention, FIGS. 2 and 3 are signal waveform diagrams for explaining the operation of the first embodiment, and FIG. 4 is a diagram of the present invention. FIG. 5 is a block diagram of an optical pulse receiving circuit showing a second embodiment, and FIG.
FIG. 6 is a block diagram of an optical pulse receiving circuit showing an embodiment, FIG. 6 is a block diagram of a signal receiving circuit showing a fourth embodiment of the present invention,
FIG. 7 is a block diagram of an optical pulse receiving circuit showing a fifth embodiment of the present invention, FIG. 8 is a block diagram showing a conventional example, FIG. 9 is a waveform diagram showing the operation of the conventional example, and FIG. FIG. 7 is a block diagram showing a conventional example of FIG. Explanation of symbols 1 ... Input terminal, 2 ... Buffer, 3 ... Voltage comparator,
A: Automatic threshold control circuit, 11 ... Voltage dividing circuit, 12 ... Reference voltage generator, 13 ... Buffer, 14 ... Peak hold circuit, 20 ... Optical transmission medium, 21 ... Photodiode, 22 ...
… Voltage conversion resistor, 24 …… Non-inverting amplifier circuit, 25 …… Signal receiving circuit, 26 …… Voltage comparator, 28 …… Voltage dividing circuit, 29 ……
Non-inverting amplifier circuit, 30 ... Peak hold circuit, 31 ... Reference voltage generator, 41 ... Transimpedance amplifier,
44 ... Inversion amplification circuit, 45 ... Voltage division circuit, 47 ... Inversion amplification circuit, 3 '... Voltage comparator, 53 ... Voltage division circuit, 54 ... Reference voltage generator, 55 ... Comparator, 61 ... Current-voltage converter, 62 ... Amplifier, 63 ... Signal receiving circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Matsuda 1-2-9 Hachiman-cho, Higashi-Kurume City, Tokyo Inside Optec Diddy Melco Laboratories, Inc. (72) Inventor Shigeru Okayasu Hachiman, Higashi-Kurume City, Tokyo 1-29, Machi Optec Diddy Melco Laboratories, Inc. (72) Inventor Jiro Katsuhara 1-2-2 Wadazakicho, Hyogo-ku, Hyogo Prefecture Mitsubishi Electric Co., Ltd. (72) Invention Toshio Nakatani 1-2-2 Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Mitsubishi Electric Corporation Control Works

Claims (5)

[Claims] 1. An automatic threshold control circuit (A) for supplying a signal obtained by superimposing a minute voltage to a divided value of an input signal voltage to a peak hold circuit (14) to obtain a threshold voltage, and the automatic threshold control circuit ( A signal receiving circuit comprising a voltage comparator (3) for comparing the threshold voltage of A) with the input signal voltage. 2. A peak hold circuit (14) for an input signal voltage.
An automatic threshold control circuit (A) that divides the voltage peak-held in step 1 to obtain a threshold voltage, and a voltage comparator (3 ') that compares the threshold voltage of the threshold control circuit (A) with the input signal voltage, A cutoff means (55) for comparing the peak hold voltage of the peak hold circuit (14) with a minute voltage, and cutting off the output of the voltage comparator (3 ') when the peak hold voltage is less than the minute voltage. A signal receiving circuit characterized by being provided. 3. A photoelectric conversion element (21) for converting an optical signal into a current signal, and a current-voltage converter (22) for converting a current signal output from the photoelectric conversion element (21) into a voltage signal. ,
An amplifier (23) for amplifying the output voltage of the current-voltage converter
And a signal receiving circuit (25) for comparing the output voltage of the amplifier (23) with a threshold voltage, the signal receiving circuit (25) An automatic threshold control circuit (A) that supplies a signal obtained by superimposing a minute voltage to a divided voltage to a peak hold circuit (30) to set a threshold voltage, a threshold voltage of the automatic threshold control circuit (A), and the amplifier ( An optical pulse receiving circuit comprising a voltage comparator (26) for comparing the output voltage of 23). 4. A photoelectric conversion element (21) for converting an optical signal into a current signal, and a current-voltage converter (41) for converting a current signal output from the photoelectric conversion element (21) into a voltage signal, In an optical pulse receiving circuit comprising an amplifier (44) for amplifying the output voltage of the current-voltage converter (41) and a signal receiving circuit for comparing the output voltage of the amplifier (44) with a threshold voltage, the signal The receiving circuit is the current-voltage converter (41).
Automatic threshold control circuit (A) that amplifies a signal obtained by superimposing a minute voltage on the divided voltage value of the output voltage and supplies it to the peak hold circuit (30) as a threshold voltage, and the automatic threshold control circuit (A) And a voltage comparator (26) for comparing the output voltage of the amplifier (44) with the threshold voltage of the optical pulse receiving circuit. 5. A photoelectric conversion element (21) for converting an optical signal into a current signal, a current-voltage converter (61) for converting a current signal output from the photoelectric conversion element (21) into a voltage signal, An optical pulse receiving circuit comprising an amplifier (62) for amplifying the output voltage of the current-voltage converter (61) and a signal receiving circuit (63) for comparing the output voltage of the amplifier (62) with a threshold voltage. The signal receiving circuit (63) includes the amplifier (62)
And a voltage for comparing the threshold voltage of the automatic threshold control circuit (A) with the output voltage of the amplifier (62). A comparator (3 ') and a shutoff means (55) for shutting off the output of the voltage comparator (3') when the peak hold voltage and the minute voltage are compared and the peak hold voltage is less than the minute voltage. An optical pulse receiving circuit comprising: