JPH0479525A - Signal reception circuit and optical pulse reception circuit using the same - Google Patents

Abstract

PURPOSE:To prevent malfunction by using an automatic threshold control circuit so as to apply peak-hold to a signal voltage superimposing a minute voltage to a divided input signal voltage using the peak hold value as a threshold voltage and comparing the threshold voltage with an input signal voltage at a voltage comparator, thereby eliminating the influence of noise or the like. CONSTITUTION:A voltage resulting from superimposing a minute voltage onto a divided input signal voltage at an automatic threshold level control circuit A is fed to a peak-hold circuit 14, in which the voltage is subjected to peak hold and a threshold voltage is obtained. Thus, when the fluctuation of the input signal voltage is generated, the threshold voltage is controlled so as to be a divided voltage compared at a voltage comparator 3 in response to a level change when the level fluctuation of the input signal voltage takes place, the production of pulse width distortion resulting from level fluctuation of the input signal voltage is prevented and a threshold voltage in response to a very small voltage is generated even at non-signal through the superimposition of the minute voltage. Thus, the influence due to noise or the like is eliminated to prevent malfunction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a signal receiving circuit that reproduces an output signal without distortion regardless of amplitude fluctuations in an input signal voltage, and an optical pulse receiving circuit using the same.

[Conventional technology]

Conventionally, this type of signal receiving circuit is known to have the configuration shown in FIG. 8. In the figure, 1 is an input terminal to which an input signal voltage is input; The input signal voltage 7.4 is supplied to the compared voltage input terminal of the voltage comparator 3 via the buffer 2, and the threshold voltage from the threshold voltage generation circuit 4 is supplied to the comparison reference voltage terminal of the voltage comparator 3. ■1 is input. Here, the threshold voltage generation circuit 4 divides the power supply voltage terminal (2) using a resistor 5 and a variable resistor 6 to output a threshold voltage (2).

Then, the voltage comparator 3 compares the input signal voltage VIN and the threshold voltage (2), and outputs an output signal voltage obtained by regenerating the input signal voltage.

By the way, in general, when a pulse signal is transmitted to a signal receiving circuit via a transmission medium, the original rectangular signal wave is blunted and attenuated by the transmission medium.

Ru. Therefore, the input signal voltage received by the signal receiving circuit is
12. varies greatly depending on the distance and characteristics of the transmission medium, and the input signal voltage Vllll VIN shown in Fig. 9 ta+
Level fluctuations occur as shown in 2.

As described above, when the input signal voltage input to the input terminal 1 of the signal receiving circuit fluctuates, the threshold voltage V generated by the threshold voltage generating circuit 4 changes. When set in the initial state, it remains a constant value thereafter, so the output signal voltage V output from the voltage comparator 3. , 11 is the input signal voltage ■1 with a large level
81, the on-state pulse width becomes a wide pulse width TWI, as shown in FIG. 9 (bj), and conversely, when the input signal voltage VIN2 has a small level, as shown in FIG. 9 (tc+), The pulse width of the on-state is a pulse width TW2 narrower than the pulse width TWI.

As a result, TwI
There was a problem in that pulse width distortion (variation) of 21) occurred in T.

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

This signal receiving circuit supplies the output signal of the buffer 2 to an automatic threshold value control circuit 7 to change the threshold voltage VT according to the input signal voltage. This automatic threshold control circuit 7
supplies the output voltage of buffer 2 to capacitor 9 via diode 8, holds the peak of the voltage by subtracting the voltage drop of diode 8 with capacitor 9, and divides this hold voltage by 1/2 with resistors R3 and R2. The voltage is divided into a threshold voltage (7), which is supplied to the comparison reference voltage input terminal of the voltage comparator 3.

[Problem to be solved by the invention]

However, in the conventional signal receiving circuit shown in FIG. 10, by setting the voltage that is 1/2 of the peak voltage of the input signal voltage as the threshold voltage ■7, the threshold voltage ■1 depends on the input signal voltage. Since the pulse width distortion of the output signal voltage due to fluctuations in the input signal voltage can be reduced, the voltage drop of the diode is large (for example, in an optical pulse receiving circuit that handles minute voltages). There was an unresolved problem that it could not be applied and the dynamic range could not be very large.

Furthermore, when there is no signal, the compared voltage of the voltage comparator 3 becomes equal to the comparison reference voltage, which causes malfunction due to the influence of noise, which is an unresolved problem.

Therefore, the present invention focuses on the unresolved problems of the conventional example described above, and can be applied even to signal receiving circuits that handle minute voltages, and prevents malfunctions due to noise etc. when there is no signal. The object of the present invention is to provide a signal receiving circuit that does not require a signal receiving circuit, and an optical pulse receiving circuit using the same.

[Means to solve the problem]

In order to achieve the above object, the signal receiving circuit according to claim (1) provides an automatic threshold value control in which a signal obtained by superimposing a minute voltage on a divided voltage value of an input signal voltage is supplied to a peak hold circuit to obtain a threshold voltage. The present invention is characterized in that it includes a circuit and a voltage comparator that compares the threshold voltage of the automatic threshold side WJm path and the input signal voltage.

The optical pulse receiving circuit according to claim (2) further includes: an automatic threshold control circuit that divides a voltage obtained by peak-holding an input signal voltage in a peak hold circuit to obtain a threshold voltage; a voltage comparator that compares the input signal voltage; and a cutoff means that compares the peak hold voltage of the peak hold circuit with a minute voltage and cuts off the output of the voltage comparator when the peak hold voltage is less than the minute voltage. It is characterized by having the following.

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 signal that converts the current signal output from the photoelectric conversion element into a voltage signal.
An optical pulse receiving circuit comprising a voltage converter, 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, the signal receiving circuit comprising: an automatic threshold control circuit that supplies a signal obtained by superimposing a minute voltage on a divided voltage value of the output voltage of the amplifier to a peak hold circuit to obtain a threshold voltage; and a threshold voltage of the automatic threshold control circuit and an output voltage of the amplifier. It is characterized by consisting of a voltage comparator that compares the

Furthermore, the optical pulse receiving circuit according to claim (4) includes:
A photoelectric conversion element that converts an optical signal into a current signal, a current-voltage converter that converts the 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, the signal receiving circuit superimposing a minute voltage on a divided voltage value of the output voltage of the current-voltage converter. and a voltage comparator that compares the threshold voltage of the automatic threshold control circuit with the output voltage of the amplifier. It is characterized by

Furthermore, the optical pulse receiving circuit according to claim (5) comprises:
A photoelectric conversion element that converts an optical signal into a current signal, a current-voltage converter that converts the 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. , a signal receiving circuit that compares the output voltage of the amplifier with a threshold voltage, and the signal receiving circuit is an automatic pulse receiving circuit that divides a voltage obtained by peak-holding the amplified output of the amplifier to obtain the threshold voltage. a threshold control circuit; a voltage comparator that compares the threshold voltage of the automatic threshold control circuit with the output voltage of the amplifier; and a voltage comparator that compares the peak hold voltage of the peak hold circuit with a minute voltage, and determines that the peak hold voltage is a minute voltage. and a cutoff means for cutting off the output of the voltage comparator when the voltage is lower than the voltage.

[Effect]

In the signal receiving circuit according to claim 11, the automatic threshold control circuit supplies a voltage obtained by superimposing a minute voltage on the divided voltage of the input signal voltage to the peak hold circuit, holds the peak, and sets it as the threshold voltage. When a level change occurs in the input signal voltage, the threshold voltage is controlled to be a predetermined divided voltage value of the voltage amplitude to be compared according to the level change. In addition to preventing pulse width distortion from occurring, the superimposed microvoltage allows a threshold voltage to be generated according to the microvoltage even when there is no signal, eliminating the effects of noise and other factors. This can eliminate malfunctions.

Further, in the signal receiving circuit according to claim (2), the input signal voltage is peak held by the peak hold circuit,
Since the hold voltage is divided and used as the threshold voltage,
The present invention is designed to prevent the occurrence of pulse width distortion due to level fluctuations in the input signal voltage, and to compare the peak hold voltage and the minute voltage with the cutoff means and cut off the output of the voltage comparator when the former is lower than the latter. Therefore, it is possible to eliminate the influence of noise and the like when there is no signal, thereby eliminating malfunctions.

Furthermore, in the optical pulse receiving circuit according to claim (3), the optical signal is converted into a current signal by a photoelectric conversion element, this is converted into a voltage signal by a current-voltage conversion circuit, and this is amplified by an 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 fluctuations in the output pulse width due to changes in the light intensity of the optical signal, and also to prevent the output pulse width from changing. Malfunctions can be eliminated by removing the effects of noise and the like on signals.

Furthermore, in the optical pulse receiving circuit according to claim (4), since the voltage signal converted into a voltage signal by the current-voltage conversion circuit is supplied to the automatic threshold control circuit, the optical pulse receiving circuit according to claim (4)
The only difference from 3) is whether the amplified voltage is supplied to the automatic threshold control circuit or amplified within the automatic threshold control circuit, so that the same effect as above can be obtained.

Furthermore, in the optical pulse receiving circuit according to claim (5), the optical signal is converted into a current signal by a photoelectric conversion element, this is converted into a voltage signal by a current-voltage conversion circuit, and this is amplified by an amplifier. Since the voltage signal is supplied to the signal receiving circuit similar to claim (2) to generate the threshold voltage, it is possible to prevent fluctuations in the output pulse width due to changes in the light intensity of the optical signal, and Malfunctions can be eliminated by removing the effects of noise when there is no signal.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

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

In the figure, 1 is a pulsed input signal voltage V via a transmission medium.
This is an input terminal to which IN is supplied, and the input signal voltage 1.4 inputted to this input terminal 1 is inputted to the compared voltage terminal of the voltage comparator 3 via the buffer 2 .

On the other hand, the input signal voltage VIN output from the buffer 2 is supplied to the automatic threshold control circuit A and the voltage dividing circuit 11. The voltage dividing circuit 11 is composed of resistors R and R2, and at the connection point between the resistors R+ and R2, there is a very small input offset voltage V which is almost negligible compared to the input signal voltage VIH from the reference voltage generator 12. , is supplied, and this minute input offset voltage V. S is superimposed on the divided voltage value of the input signal voltage VIN.

Then, the superimposed signal voltage output from the connection point between resistors R+ and R2 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, a diode 15 and a hold capacitor 16 are connected in series between the output side and the ground, and a resistor 17 is connected in parallel with the capacitor 16. It has a non-inverting operational amplifier 18 connected to the capacitor 1.
The connection point between the capacitor 16 and the resistor 17 is connected to the inverting input side of the operational amplifier 18, and the peak hold voltage output from the connection point between the capacitor 16 and the resistor 17 is used as the threshold voltage (a) and the comparison reference voltage of the voltage comparator 3. input to the terminal.

Next, the operation of the first embodiment will be explained. Now, suppose that an input signal voltage ■1□ with rounding and level fluctuation is input to the input terminal 1 via the transmission medium. It is input to the voltage-to-be-compared terminal, and the voltage divider circuit 11
Since the voltage is supplied to the voltage, the voltage is divided to 1/N by the voltage dividing circuit 11. On the other hand, this voltage dividing circuit 11 includes a reference voltage generator 12.
The small input offset voltage V from , and this minute input offset voltage VO3 is the input signal voltage V
Since it is superimposed on the voltage division value VIN/N of IN, voltage division circuit 1
1 output voltage■. is, VD ==V IN/N + Vos#V IN/
N ...---(11), and this output voltage is supplied to the peak hold circuit 14 via the buffer 13, so that the output voltage is The peak value is held for a holding time equal to the threshold voltage Vt and is supplied to the comparison reference voltage terminal of the voltage comparator 3. Therefore, when the input signal voltage VIN from the voltage comparator 3 exceeds the threshold voltage v7, Output voltage {circle around (2)} with logical value "l".U7 is output.

By the way, as mentioned above, the input signal voltage input to the input terminal 1 via the transmission medium is rounded and accompanied by level fluctuations, so for example, as shown by the solid line in FIG. 2 (11), , input signal voltage V with a large level,
N, is input to input terminal 1, voltage divider circuit 11
The output voltage VD output from the output voltage VD becomes a large value and is supplied to the peak hold circuit 14 via the buffer 13. Therefore, the peak value held by the peak hold circuit 14 depends on the large level of the input signal voltage VIN+. As shown in Figure 2 (al), the input signal voltage VIN+
The peak value of is substituted into the above equation (11), and this is input as the threshold voltage ■1 to the comparison reference voltage terminal of the voltage comparator 3, so the output voltage of this voltage comparator 3 V.tl
TI is the input signal voltage VI, as shown in Figure 2 (bl)
The logic value "0" is maintained from zero until N+ exceeds the threshold voltage Vt+, and at the time t when N+ exceeds the threshold voltage VTI, it is inverted to the logic value "1", and then becomes less than the threshold voltage V y ( At time 1t, the logic value is again inverted to "0".

On the other hand, the input terminal 1 is connected to the input terminal 1 as shown in FIG.
When a small level input signal voltage VIN□ is input, the level of the output voltage VD of the voltage divider circuit 11 also decreases, and the threshold voltage VT2 output from the peak hold circuit 14 also decreases as shown in FIG. The value is small as shown by the broken line.For this reason, the output voltage Vout of the voltage comparator 3
As shown in FIG. 2 (C1), z is inverted to the logic value "1" at time t, and to logic value "0" at time t2, similar to the high-level input signal voltage VINI. Therefore, a pulse output voltage with the same pulse width T and 1 can be obtained regardless of level fluctuations of the input signal voltage V I N, and pulse width distortion can be reliably prevented.

In addition, when there is no signal when the input signal voltage V 1 H is zero, the voltage dividing circuit 11 outputs a small voltage of only the small input offset voltage Vo3, which is held at its peak in the peak hold circuit 14 and set as the threshold voltage. vT, this threshold voltage Vt becomes a value higher by the minute input offset voltage VOS as shown in No. 311(a), and this is input to the comparison reference voltage terminal of the voltage comparator 3, so that the sheet metal input signal voltage Even if low-level noise etc. is mixed into VHH, the output voltage of voltage comparator 3 ■. U
T maintains the logical value "O" as shown in FIG. 3(b),
The output voltage of voltage comparator 3 ■ due to the influence of noise etc. I
Malfunctions such as IT inversion will not occur.

Next, a second embodiment of the present invention will be described based on FIG. 4.

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, a light pulse transmitted through an optical transmission medium 20 such as an optical fiber is input to a photodiode 21 as a photoelectric conversion element connected between a positive power terminal V and ground. and this photodiode 21
The current is controlled according to the light intensity of the light pulse received by the
This current is converted into a voltage signal by a voltage conversion resistor 22 connected in series with the photodiode 21.

This voltage signal is connected to the operational amplifier 23 and the resistor R11゜R1□
The signal is amplified by a non-inverting amplifier circuit 24 and input to a signal receiving circuit 25.

The signal receiving circuit 25 includes a voltage comparator 26 to which the amplified output VIN from the non-inverting amplifier circuit 24 is input to the compared voltage terminal, and an automatic threshold control circuit A. a voltage dividing circuit 27 having resistors R1 and R4 to which the amplified output Vll of the amplifier circuit 24 is supplied;
Operational amplifier 2 to which the output voltage of this voltage divider circuit 27 is input
8, a resistor R+s, and a resistor R16, and the amplified output of this non-inverting amplifier circuit 29 is input, and the peak hold value is set as a threshold voltage to the voltage comparator 2.
Peak hold circuit 3 outputs to the comparison reference voltage terminal of 6.
0.

Here, on the inverting input side of the non-inverting amplification diagram ¥829, there is a minute input offset voltage (■) of the reference voltage generator 31, which has a variable resistor VR connected between the positive and negative power supplies. .

is entered. Moreover, the peak hold circuit 30 is
Like the peak hold circuit 14 of the first embodiment described above, it is composed of an operational amplifier 32, a diode 33, a capacitor 34, and a resistor 35.

Next, the operation of the second embodiment will be explained. Optical transmission medium 2
The light pulse from 0 passes through the photodiode 21 and the resistor 22.
It is converted into a voltage by be done. Therefore, the output voltage (2) of the voltage dividing circuit 27 becomes VINX (1/M).

This divided voltage is input to the non-inverting amplifier circuit 29, where it is multiplied by M/N, and a minute input offset voltage (2) is input to the inverting input side of the non-inverting amplifier circuit 29. Superimpose S. Therefore, the output voltage VA of the non-inverting amplifier circuit 29 is νA=(v+s/q))X(M/
K)+Vos= (VIN/K)+Vos”V+s
/K---f21.

The output voltage VA represented by (2) 2 is the first
Since the value is equal to the output voltage V of the voltage divider circuit 11 inputted to the peak hold circuit 14 in the embodiment, the same effect as in the first embodiment can be obtained, and the optical pulse It is possible to obtain a reception output that does not cause pulse width distortion regardless of changes in the optical intensity of the optical transmission medium 20, variations in the coupling loss of the optical connector, or the emission power of the optical transmitter. Since the threshold voltage is fixed to the offset voltage of the non-inverting amplifier circuit 29 when there is no signal, it is easy to detect no signal and eliminate malfunctions due to noise etc. can.

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

In this third embodiment, a transimpedance amplifier 41 is applied in place of the resistor 22 as the current-voltage conversion means in the second embodiment, and corresponding parts to those in FIG. 4 are designated by the same reference numerals. A detailed explanation thereof will be omitted.

That is, as shown in FIG. 5, in the configuration of FIG. 4, the resistor 22 is omitted and a resistor R11 is inserted between the inverting input side and the output side of the anode of the photodiode 21 that constitute the transimpedance amplifier 41. It is connected to the inverting input side of the operational amplifier 42, and the output voltage of the transimpedance amplifier 41 is inverted and amplified by the inverting amplifier circuit 44, which is composed of the operational amplifier 43 and resistors R4□ and R43, to the compared voltage terminal of the voltage comparator 25. At the same time, it is also supplied to the voltage dividing circuit 45 of the automatic threshold value control circuit A.

The voltage dividing circuit 45 is composed of resistors Raa and R4, and this divided voltage (2). However, the operational amplifier 46 and the resistors R46 to R4
11, and the output voltage 4 of this inverting amplifier circuit 47 is supplied to the peak hold circuit 3.
0, and a small manual offset voltage ■ from the reference voltage generator 31 is input to the non-inverting input side of the inverting amplifier circuit 47. , is configured to be input.

According to this 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,
Further, the amplified output VIN which has been inverted and amplified N times by the inverting amplifier circuit 44 is input to the compared voltage terminal of the voltage comparator 25.

2 ] On the other hand, the output voltage of the transimpedance amplifier 41 (
=■, do/N) is divided into 1/M by the voltage dividing circuit 45, and the divided voltage ■, is ■. =VIN/N·(1/M) and is supplied to the inverting input side of the operational amplifier 46 of the inverting amplifier circuit 47. This inverting amplifier circuit 47 multiplies it by N·M/, and the minute input offset value pressure ■ is input to its inverting input side. , is superimposed. Therefore, the output voltage vA of the inverting amplifier circuit 47 is VA= (V+s/(N'M)) X (N'
M/K) +Vos=(VIN/K) +Vos'V
+s/K = --...i3), 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 VT.

Therefore, the output voltage vA expressed by the above equation (3) of the inverting amplifier circuit 47 input to the peak hold circuit 30 has exactly the same value as the above equation (2) in the second embodiment, so The same effects as in the second embodiment can be obtained.

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

This fourth embodiment shows a modification of the signal receiving circuit of the first embodiment, and corresponding parts to those in FIG. 1 are denoted by the same reference numerals, and detailed explanation 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 changed to the compared voltage of the voltage comparator 3'' with a strobe terminal. In addition to supplying the voltage to the peak hold circuit 14 to the automatic threshold value control circuit, the peak hold voltage (2) of the peak hold circuit 14 is supplied to the voltage dividing circuit 53 composed of resistors 51 and 52. The divided voltage of the voltage dividing circuit 53 is supplied as a threshold voltage 1 to the comparison voltage terminal of the voltage comparator 3 with a strobe terminal, and the peak hold voltage 2 of the peak hold circuit 14 is supplied as the threshold voltage 1 from the reference voltage generator 54. The minute input offset voltage V.S is input to the other end of the comparator 55, and the enable signal output from the comparator 55 when y<VOS is the strobe terminal 3a of the voltage comparator 3'. is configured to be input.

According to this fourth embodiment, the peak hold voltage V obtained by peak holding the input signal voltage in the peak hold circuit 14 is
P is divided by the voltage dividing circuit 53 and supplied as the threshold voltage ■1 to the comparison voltage terminal of the voltage comparator 3°, which is much faster than when dividing the voltage drop caused by the diode as in the conventional example. It is possible to have a wide range, and when the peak hold value V of the input signal voltage is compared with the minute input offset value V03, V<V. , an enable signal is input to the strobe terminal 3a of the voltage comparator 3', so if the input signal voltage is zero, the voltage comparator 3' is always in an inactive state and there is no signal. Therefore, the same effects as in the first embodiment described above can be obtained.

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

In this fifth embodiment, the signal receiving circuit of the fourth embodiment is applied to an optical pulse receiving circuit.

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

According to the fifth embodiment, the photodiode 22 receives an optical pulse transmitted through the optical transmission medium 21, 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, so that the signal receiving circuit 63 can obtain a receiving output that does not cause pulse width distortion regardless of changes in the optical intensity of the optical pulse. , the peak hold value ■ of the peak hold circuit 14 of the signal receiving circuit 63 when there is no optical pulse signal.

and small input offset voltage■. By comparing the voltage with S and supplying an enable signal to the strobe terminal 3a of the voltage comparator 3', the voltage comparator 3' is put into a non-differential state and its output is made into a no-signal state, thereby eliminating the influence of noise, etc. be able to.

In addition, in the fourth and fifth embodiments described above, the case where the voltage comparator 3 with a strobe terminal was applied as the voltage comparator was explained, but the present invention is not limited to this.
An ordinary voltage comparator may be used, a gate circuit may be provided on the output side of the 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.

〔Effect of the invention〕

As described above, according to the signal receiving device according to claim (1), the automatic threshold control circuit peak-holds the signal voltage obtained by superimposing a minute voltage on the divided voltage value of the input signal voltage, and this peak hold value is Since the threshold voltage is set as a direct voltage and this threshold voltage is compared with the input signal voltage using a voltage comparator,
It is possible to obtain a received signal with no pulse width distortion regardless of level fluctuations in the input signal voltage, and the threshold voltage is at a very high level when there is no signal when the input signal voltage is zero. This provides the effect of reliably eliminating malfunctions.

Further, according to the signal receiving circuit according to claim (2), the input signal voltage is peak-held by the peak-hold circuit, this is divided into a threshold voltage, and the peak-hold voltage is compared with a minute voltage. Since it is determined that there is no signal when the hold voltage is lower than the minute voltage and the output of the voltage comparator is cut off, it is possible to obtain the same effect as in claim (1).

Furthermore, according to the optical pulse receiving circuit according to claim (3), the optical signal is converted into a current value by the photoelectric conversion element, and the value converted into a voltage value by the current-voltage conversion circuit is amplified and the voltage is compared. By inputting it to the compared voltage terminal of the device and supplying it to the automatic threshold control circuit described above, it is possible to know the received signal without pulse width distortion regardless of fluctuations in the optical intensity of the optical pulse input to the photoelectric conversion element. In addition, since the threshold voltage is at a level that is as high as the i voltage when there is no optical pulse and no signal, it is possible to reliably eliminate malfunctions due to the influence of noise or the like.

Furthermore, according to the optical pulse receiving circuit according to claim (4), the value converted into a voltage value by the current-voltage conversion circuit is supplied to the automatic threshold value control circuit, and the value is amplified within the automatic threshold value control circuit to determine the threshold value. Since the voltage is obtained, the same effect as in claim (3) above can be obtained as a result.

Furthermore, according to the optical pulse receiving circuit according to claim (5), the value converted into a voltage value by the current-voltage conversion circuit is amplified by an amplifier and supplied to the signal receiving circuit according to claim (2). Therefore, the same effects as in claims (3) and (4) can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a signal receiving circuit according to 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 block diagram of a signal receiving circuit according to a first embodiment of the present invention. FIG. 5 is a block diagram of the optical pulse receiving circuit showing the second embodiment.
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. 10 is another example. FIG. 2 is a block diagram showing a conventional example. Explanation of symbols 1- Input terminal, 2- Buffer, 3 Voltage comparator, A-
automatic threshold control circuit, 11 - voltage divider circuit, 12 - reference voltage generator, 13 - buffer, 14 peak hold circuit,
20... Optical transmission medium, 21-... Photodiode, 2
2-voltage conversion resistor, 24-non-inverting amplifier circuit, 25-signal receiving circuit, 26--voltage comparator, 28-voltage dividing circuit,
2-1 non-inverting amplifier circuit, 30-peak hold circuit, 31=-reference voltage generator, 41-1-lance impedance amplifier, 44-inverting amplifier circuit, 45-voltage divider circuit, 47-inverting amplifier circuit, 3゛−
Voltage comparator, 53 - voltage divider circuit, 54 - reference voltage generator, 55 - comparator, 61 - current-voltage converter, 62 -
Amplifier, 63-・Signal receiving circuit.

Claims (5)

[Claims] (1) An automatic threshold control circuit (A) that supplies a signal in which a minute voltage is superimposed on a divided voltage value of an input signal voltage to a peak hold circuit (14) to obtain a threshold voltage;
A signal receiving circuit comprising: a voltage comparator (3) that compares the threshold voltage of A) with the input signal voltage. (2) an automatic threshold control circuit (A) that divides the voltage peak held by the peak hold circuit (14) to obtain a threshold voltage; and the threshold voltage of the threshold control circuit (A) and the input signal voltage; and a voltage comparator (3') that compares the peak hold voltage of the peak hold circuit (14) with the minute voltage, and when the peak hold voltage is less than the minute voltage, the voltage comparator (3') compares the peak hold voltage of the peak hold circuit (14) with the minute voltage. ) A signal receiving circuit characterized in that it is equipped with a cutoff means (55) for cutting off the output of the signal receiver. (3) Photoelectric conversion element (21
), a current-voltage converter (22) that converts the current signal output from the photoelectric conversion element (21) into a voltage signal,
an amplifier (23) that amplifies the output voltage of the current-voltage converter;
) and a signal receiving circuit (25) that compares the output voltage of the amplifier (23) with a threshold voltage.
an automatic threshold control circuit (A) that supplies a signal obtained by superimposing a minute voltage on the partial voltage value of the output voltage of 3) to a peak hold circuit (30) to obtain a threshold voltage; and the automatic threshold control circuit (A).
An optical pulse receiving circuit comprising: a voltage comparator (26) that compares the threshold voltage of the amplifier (23) with the output voltage of the amplifier (23). (4) Photoelectric conversion element (21
), a current-voltage converter (41) that converts the current signal output from the photoelectric conversion element (21) into a voltage signal, and an amplifier (44) that amplifies the output voltage of the current-voltage converter (41). ) and a signal receiving circuit that compares the output voltage of the amplifier (44) with a threshold voltage, the signal receiving circuit comprising:
an automatic threshold control circuit (A) that amplifies a signal obtained by superimposing a minute voltage on the partial voltage value of the output voltage of 1) and supplies it to a peak hold circuit (30) to obtain a threshold voltage; An optical pulse receiving circuit comprising: a voltage comparator (26) that compares the threshold voltage of A) with the output voltage of the amplifier (44). (5) A photoelectric conversion element that converts an optical signal into a current signal;
1), a current-voltage converter (61) that converts a current signal output from the photoelectric conversion element (21) into a voltage signal, and an amplifier (62) that amplifies the output voltage of the current-voltage converter (61). ) and a signal receiving circuit (63) that compares the output voltage of the amplifier (62) with a threshold voltage, wherein the signal receiving circuit (63) is configured to detect the amplified output of the amplifier (62). an automatic threshold control circuit (A) that divides the peak-held voltage into a threshold voltage, and a threshold voltage of the automatic threshold control circuit (A) and the amplifier (62).
a voltage comparator (3') that compares the output voltage of the peak hold voltage with the minute voltage;
An optical pulse receiving circuit characterized in that it is equipped with a cutoff means (55) for cutting off the output of the light pulse receiving circuit.