JP2005110041A - Optical signal receiving apparatus and dc offset adjusting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical signal receiving apparatus with a wide dynamic range and to provide a DC offset adjusting circuit. <P>SOLUTION: The optical signal receiving apparatus is provided with: a photo-electric transducer; and an electric signal amplifier integrated circuit that supplies a power voltage to the photo-electric transducer and processes an output signal from the photo-electric transducer. The electric signal amplifier integrated circuit is provided with: a current detection circuit that comprises a first current mirror circuit for detecting a quantity of current flowing into the photo-electric transducer and outputs a first output current corresponding to the detected current quantity; an amplifier circuit that amplifies the output signal of the photo-electric transducer; and a DC absorption circuit that absorbs a DC corresponding to the first output current from the output signal of the photo-electric transducer inputted to the amplifier circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical signal receiving apparatus and a DC offset adjustment circuit.

  An optical communication device receives a transmitted optical signal and converts it into an electrical signal using a photoelectric conversion element typified by a photodiode.

  For example, an optical communication device is configured using a PIN photodiode and a transimpedance amplifier circuit. In general, PIN type photodiodes and transimpedance type amplifiers are manufactured in different processes, so that they are manufactured as individual elements, that is, as integrated circuits of photodiode element chips and amplifiers, without using a single chip, and using bonding wires or the like. It will be electrically connected.

  An optical communication apparatus needs to operate in a wide dynamic range from a minute optical signal to a large optical signal. In addition, the DC current component included in the signal output from the photodiode is small when the optical signal is small, and a large DC current is generated when the optical signal is large. Therefore, the DC current also changes according to the input signal power. Will do.

  Since this DC current flows into the integrated circuit (amplifier), the dynamic range is limited by fluctuations in the bias level on the amplifier side.

  In order to cope with such a problem, a method (DC offset adjustment circuit) for removing the DC current component of the photodiode has been proposed. For example, in Japanese Patent Laid-Open No. 2000-269541, a power supply voltage supply means for a photodiode is provided in an integrated circuit for electric signal amplification to supply power to the photodiode from the integrated circuit. , And a technique using a system in which a DC current is absorbed from an output current of a photodiode by a DC current absorption circuit according to the detection result, and a DC current is not allowed to flow into an electric signal amplifier circuit.

  The current absorption circuit described in Japanese Patent Application Laid-Open No. 2000-269541 includes a voltage comparator and a current absorption element. This circuit has a large number of elements and is complicated, and has problems such as an increase in chip area, an increase in current consumption, and an error in absorption current.

  Further, when the absorption current is increased, the DC current cannot be absorbed due to the voltage drop in the current absorption circuit, and there is a fear that the normal operation of the amplifier cannot be maintained.

Further, since the comparator has a current limit value, the maximum absorption current is determined by the comparator, so that there is a problem that the application is limited by the performance of the comparator.
JP 2000-269541 A

  The present invention has been made in consideration of the above points, and an object thereof is to provide an optical signal receiving apparatus and a DC offset adjustment circuit having a large dynamic range.

The present invention relates to an optical signal receiving apparatus comprising: a photoelectric conversion element; and an electric signal amplification integrated circuit that supplies a power supply voltage to the photoelectric conversion element and processes an output signal from the photoelectric conversion element.
The electric signal amplification integrated circuit detects a current amount flowing into the photoelectric conversion element, and a current detection circuit including a first current mirror circuit that outputs a first output current corresponding to the detected current amount An electric signal amplification circuit for amplifying an output signal of the photoelectric conversion element; and a second current mirror circuit for turning back a second output current corresponding to the first output current, and is input to the amplification circuit. An optical signal receiving apparatus comprising: a DC current absorption circuit that absorbs the second output current from an output signal of the photoelectric conversion element.

  By combining two current mirror circuits, it is possible to realize absorption of a DC current with a circuit having a simpler configuration than when a comparator is used. In addition, since the current mirror circuit does not limit the absorption current when a comparator is used, it is possible to suppress fluctuations in the bias level of the amplifier circuit, particularly when a large optical signal is input, and a wide dynamic range. The amplifier circuit can operate in response to the optical signal.

  The present invention also relates to an electric signal amplifier circuit that amplifies an output signal including a DC offset current from a photoelectric conversion element, a radio frequency processing unit of a radio device, and the like; DC offset adjustment comprising: a current absorption circuit; and a signal blocking circuit in which a blocking amount of a signal current flowing into the DC current absorption circuit from the output signal input to the amplifier circuit is variably set. Circuit.

  An output signal from a photoelectric conversion circuit or the like is distributed in a ratio between the input impedance of the amplifier constituting the electric signal amplification circuit and the impedance of the signal blocking circuit and the DC current absorption circuit branched from the input terminal of the amplifier. In general, the input impedance of an amplifier is about 10Ω, which is extremely small compared to the impedance on the side of the current absorption circuit, which is about 1 kΩ. The predetermined amount of DC offset current is absorbed by the DC current absorption circuit. Therefore, most of the output signal (signal current) excluding this DC current flows to the amplifier.

  When the amount of DC current increases (for example, when the optical signal power increases or the RF reception signal level increases), the DC current absorption circuit can operate normally due to the voltage drop in the signal blocking circuit. It may disappear. For example, when a constant current source is used for the DC current absorption circuit, the source-drain voltage of the transistor may not be secured.

  In such a case, since a predetermined amount of DC current cannot be absorbed, a DC current component flows into the amplifier, the amplifier bias level changes, and normal operation of the amplifier cannot be ensured.

  In order to prevent such a situation, the signal blocking amount is made variable. That is, when the DC current to be absorbed is large and the voltage drop in the signal blocking circuit is large, the signal blocking amount is lowered and the voltage drop is controlled to be small. Conversely, when the amount of DC current to be absorbed is small, the S / N at the time of a small signal is ensured by increasing the amount of signal output and increasing the amount of the PD output signal flowing to the amplifier side.

  By providing such a signal blocking circuit with a variable signal blocking amount, even when the absorption current increases and the voltage level of the current absorption circuit decreases, the amplifier can be controlled by reducing the signal blocking amount. Driving in the normal operating range is possible, and the amplifier circuit can operate in response to an optical signal having a wide dynamic range.

Further, in a wireless device including an antenna; a high-frequency signal processing unit that processes an RF signal from the antenna; and a baseband processing unit that processes an output signal from the high-frequency signal processing unit:
A DC offset adjustment circuit as described above is provided between the high-frequency signal processing unit and the baseband processing unit, and is effective as a radio device that absorbs a DC offset current from the high-frequency signal processing unit.

  In particular, in the case of a direct-conversion radio that does not require an intermediate frequency processing unit, the problem of DC offset is significant, so that the application effect of the present invention is significant.

  Since the signal blocking circuit only needs a simple configuration such as a variable resistor, the circuit configuration is not complicated.

  According to the present invention, it is possible to obtain an optical signal receiving device and a DC offset adjustment circuit having a large dynamic range.

  Embodiments of the present invention will be described below.

  FIG. 1 is a functional configuration diagram showing an embodiment of the present invention. A portion surrounded by a dotted frame means the inside of the electric signal amplification integrated circuit 10. The photoelectric conversion circuit 20 is outside the electric signal amplification integrated circuit 10.

  The power supply voltage of the photoelectric conversion circuit 20 is supplied via the current detection circuit 101 inside the electric signal amplification integrated circuit 10.

  The photoelectric conversion circuit 20 receives an optical signal and outputs an electrical signal after photoelectric conversion. The output electrical signal is input to the electrical signal amplification circuit 102 inside the electrical signal amplification integrated circuit 10, is voltage amplified, and is output to the outside of the electrical signal amplification integrated circuit 10.

  In accordance with the current detected by the current detection circuit 101, DC current is absorbed by the current absorption circuit 103 from the signal supplied from the photoelectric conversion circuit 20 to the electric signal amplification circuit 102.

  The current absorption circuit 103 is connected to the signal input terminal of the electric signal amplification circuit 102 and absorbs a desired current from the input to the electric signal amplification circuit 102.

  In the present embodiment, the DC current detected by the current detection circuit is transmitted to the current absorption circuit by the current mirror circuit configuration.

  The current detection circuit 101 includes a first current mirror circuit, detects a DC current generated in the photoelectric conversion circuit 20, and outputs a current proportional to the DC current of the photoelectric conversion circuit 20.

  The current absorption circuit 103 includes a second current mirror circuit, receives an output current from the current detection circuit 101 proportional to the DC current of the photoelectric conversion circuit 20, and turns back the current proportional to the electric current amplification circuit 102. Will absorb from the input.

  Therefore, the DC current is absorbed by the current absorption circuit 103 from the input from the photoelectric conversion circuit 20 to the electric signal amplification circuit 102, and the inflow to the electric signal amplification circuit 102 can be reduced.

Therefore, it is possible to suppress the fluctuation of the bias level of the electric signal amplifier circuit 102 when a large optical signal is input, and the electric signal amplifier circuit 1 corresponds to the optical signal with a wide dynamic range.
02 can operate.

  FIG. 2 is a circuit diagram showing an embodiment of the present invention. The dotted line means the internal circuit of the integrated circuit. In the figure, M is a transistor, R is a resistor, Amp is an amplifier, and PD is a photodiode constituting the photoelectric conversion circuit 20.

  Although not shown, the PD can be grounded via a capacitor in order to stabilize the high-frequency potential.

  The transistors M1 and M2 constitute a first current mirror circuit constituting the current detection circuit 101, and the transistors M3 and M4 constitute a second current mirror circuit constituting the current absorption circuit 103.

  The source of the transistor M1 is connected to Vpd, the drain is connected to a terminal for PD power supply output, and the gate and drain are connected (diode connection).

  The source of the transistor M2 is connected to Vpd, and the gate is connected to the gate of the transistor M1. The source is connected to the drain of a transistor M3 described later.

  The diode-connected transistor M1 and the transistor M2 constituting the constant current source constitute a first current mirror circuit (current detection circuit 102).

  The drain of the transistor M3 is connected to the drain of the transistor M2, and the source is grounded (GND). The gate and drain are connected (diode connection).

  The source of the transistor M4 is grounded (GND), and the gate is connected to the gate of the transistor M3. The drain is connected to the input terminal of the amplifier Amp via the resistor R1.

  The resistor R1 is provided between the current absorption circuit 103 and the input terminal of the amplifier Amp (input terminal of the current signal amplifier circuit 102), and is provided so that the signal current is distributed to the amplifier Amp.

  The diode-connected transistor M3 and the transistor M4 constituting the constant current source form a second current mirror circuit (current absorption circuit 103).

  The electric signal amplifying circuit 102 includes an amplifier Amp and a negative feedback resistor R2, and a driving voltage Vcc is supplied to the amplifier Amp. O1 is a signal output terminal.

  Vpd is taken into the integrated circuit 10 as a PD power supply voltage, and is output to the outside of the integrated circuit 10 through the transistor M1, and the output PD power supply voltage is connected to the cathode terminal side of the PD.

  Next, circuit operation will be described.

  When an optical signal is input to the PD, an electrical signal is output to the anode terminal side of the PD by photoelectric conversion. The output electric signal is input to the electric signal amplifier circuit 102.

  The PD current detected by the transistor M1 is output to the transistor M2 constituting the current mirror, and a current proportional to the detection result is input to the transistor M3.

  The current proportional to the PD current received by the transistor M3 is converted into an absorption current approximately equal to the DC current of the PD by the transistor M4, and only the DC current is absorbed from the output current of the PD via the resistor R1.

  A signal component obtained by subtracting a current forcibly drawn by the constant current source (transistor M4) from the output signal of the PD is branched into an input to the electric signal amplifier circuit 102 and an input to the current absorption circuit and the resistor R1. The

Generally, in the negative feedback amplifier as described above, the input impedance is low (for example, about 10Ω)
On the other hand, the combined impedance (for example, about 1 kΩ) of the output impedance of the transistor M4 and the resistor R1 constituting the impedance current source branched from the input end of the electric signal amplifier circuit 102 is high (ratio of about 100 times). Therefore, it can be considered that this signal component hardly flows in the current absorption circuit 102.

  As described above, with this circuit configuration, the DC current of the PD generated at the time of optical signal reception is absorbed by the current absorption circuit, and stable operation can be obtained without flowing into the electric signal amplification circuit.

  Also, by configuring the current detection circuit and the current absorption circuit with a current mirror, an optical signal light receiving device that is simple, has high current accuracy, and can absorb a wide range of current without being limited by the DC current value generated from the PD is provided. can do.

  When a comparator is used in a current absorption circuit as in the past, it is difficult to obtain the accuracy of the comparator and an error in the current absorption amount is likely to occur.However, in the present invention, the circuit configuration is simple and high accuracy is achieved. A current absorption value can be realized. The comparator has a current limit value, and the maximum absorption current is limited by the performance of the comparator. However, in this embodiment, there is no such limit.

  FIG. 3 is a functional configuration diagram showing another embodiment of the present invention. The same numbers are assigned to the same blocks as in FIG.

  The current detection circuit 101 detects a DC current generated in the photoelectric conversion circuit 20 and outputs the detection result to the current absorption circuit 103.

  The current absorption circuit 103 is connected to a signal input terminal of the electric signal amplification circuit 102 via a signal blocking circuit 104 capable of controlling the signal blocking amount. The signal blocking circuit 104 is arranged so that the signal component of the output signal of the photoelectric conversion circuit 20 is appropriately input to the electric signal amplifier circuit 102. That is, at the branch point at the input end of the electric signal amplifier circuit 102, the branch on the current absorption circuit 103 side is set to have an appropriate impedance sufficiently high with respect to the input impedance of the electric signal amplifier circuit.

  The output terminal of the signal blocking circuit 104 is connected to the input terminal of the current / current absorption circuit 103. The signal blocking circuit 104 has a variable signal blocking amount.

  The DC current from the PD output signal is absorbed from the PD output signal via the signal blocking circuit 104 and the current absorption circuit 103. However, when the amount of absorbed current increases, the voltage drop in the signal blocking circuit 104 increases, and as a result, it may be difficult to maintain a normal bias level of the current absorbing circuit 103.

  Therefore, a configuration is adopted in which the voltage at the output terminal of the signal blocking circuit 104 (that is, the bias level of the current absorption circuit 103) is detected and the voltage drop amount in the signal blocking circuit 104 is controlled.

  That is, when the voltage drop amount in the signal blocking circuit 104 exceeds a certain reference, the signal blocking amount is increased to suppress the voltage drop amount. By performing such control, the above problem is solved.

  FIG. 4 is a circuit diagram showing an embodiment of the present invention. The same parts as those in FIG. 2 are given the same numbers, and the description thereof is omitted.

  In the circuit configuration of FIG. 2, the resistor R1 performs a signal blocking function. In FIG. 4, a variable resistor R3 is interposed in series with the resistor R1.

  When a large optical signal is input, the amount of absorbed current increases, but the voltage drop due to the resistors R1 and R3 increases correspondingly, and there is a risk that the potential necessary for the operation of the transistor M4 connected in series cannot be secured. is there.

  In order to avoid this, when the amount of absorbed current is large, the resistance value of the variable resistor R3 is lowered to suppress the voltage drop. By controlling in this way, appropriate current absorption can be performed while ensuring the operation of the transistor M4.

  Since the transistor M4 forms a constant current source, the amount of DC current absorbed does not change even if the resistance value of R3 changes.

  On the other hand, in the case of a small optical signal, the absorption current is small and there is no problem of the voltage drop. In this case, it is preferable to increase the signal blocking amount (that is, the ratio of the combined impedance of the current absorption circuit and the signal blocking circuit to the input impedance on the electric signal amplifier 102 side) in order to improve the S / N.

  Therefore, for example, the maximum resistance value of the variable resistance value may be set within a range in which the normal operation of the transistor M4 can be ensured.

  Accordingly, it is possible to solve the problem that the drain voltage of the transistor M4 constituting the current absorption circuit is lowered due to the voltage drop of the signal blocking circuit, and at the same time, when the small signal is input, the blocking amount of the signal blocking circuit is maximized. As a result, good signal amplification with less noise is possible, the amount of current absorption when a large signal is input can be increased, and a circuit with a wide dynamic range can be provided.

The circuit shown in FIG. 5 realizes such a function of the variable resistor R3 with a configuration in which the resistor R3 ′ and the transistor M5 are connected in parallel.

  In this circuit, a resistor R3 'and a transistor M5 are connected in parallel instead of the variable resistor R3 in FIG. The control terminal (gate terminal) of the transistor M5 receives a control signal (becomes a gate voltage) from the signal blocking amount control circuit 105, and the current shunted to the transistor M5 is controlled.

  The signal blocking amount control circuit 105 detects the voltage drop due to the resistors R1 and R3 ', and determines the gate potential of the transistor M5 so that this potential falls within an appropriate range.

That is, when the output signal level of the PD is low, since the S / N ratio is small, it is desired to flow the signal current to the amplifier side as much as possible. As a result, the resistance value of the parallel circuit composed of the resistor R3 ′ and the transistor M5 increases,
The amount of signal blocking increases.

  Conversely, when the output signal level of the PD is high, control is performed to increase the amount of current flowing through the transistor M5 in order to reduce the voltage drop due to the absorbed current. As a result, the resistance value of the parallel circuit composed of the resistor R3 'and the transistor M5 decreases, and the signal blocking amount decreases.

  By controlling in this way, the operation of the transistor M4 constituting the current absorption circuit 103 can be ensured.

  For example, if the amount of absorbed current is large and the resistance of the signal blocking circuit 104 is large, the voltage drop is large, and if the voltage drop is large, the voltage necessary for the operation of the transistor M4 cannot be secured. That is, the voltage between the drain and source of the transistor M4 enters the linear region from the saturation region, which is a normal operation region, and there is a possibility that the DC current cannot be normally absorbed.

  Therefore, when the amount of current absorption is excessive, it is necessary to reduce the resistance value of the signal blocking circuit 104 and reduce the voltage drop. In this embodiment, such control can be performed.

  In the case of a small signal, it is necessary to reduce the signal current flowing through the current absorption circuit 103 as much as possible in order to increase the S / N ratio, and the resistance value of the signal blocking circuit 104 is increased.

  That is, by setting a large signal blocking amount when a small signal is input and by setting a small signal blocking amount when a large signal is input, the noise characteristics are improved when the signal is small, and the current absorption function is reduced due to a voltage drop when the signal is large. Can be blocked.

  Therefore, it can operate in response to an optical signal having a wide dynamic range.

  FIG. 6 is a block diagram showing a circuit configuration of the signal inhibition amount control circuit (DC offset adjustment circuit) of the above embodiment.

  Since there is no particular limitation on the PD current detection circuit, the description is omitted.

  Further, the signal input circuit is not limited to the photoelectric conversion circuit. For example, a high-frequency signal processing unit of a radio device may be used. The present invention can be applied to anything that includes a DC offset as an output and needs to eliminate this.

  An output signal from a signal input circuit (corresponding to a signal input terminal from the photoelectric conversion circuit 20 in FIG. 5) is input to an electric signal amplifier circuit (corresponding to 102 in FIG. 5). Part of this output signal (DC current) is absorbed by a current absorption circuit (corresponding to 104 in FIG. 5) via a signal blocking circuit (corresponding to 104 in FIG. 5). In the signal blocking circuit, the signal blocking amount is adjusted by the signal blocking amount control circuit.

  The signal blocking amount control circuit includes voltage detecting means for detecting the voltage of the signal blocking means, and compares this with a reference voltage obtained from the reference voltage generating means, and generates a control signal based on the result. The means generates a control signal to be sent to the signal blocking means. In the circuit of FIG. 5, the gate voltage of the transistor M5 corresponds to the control signal.

  In this embodiment, the current detection circuit and the current absorption circuit may use a current mirror circuit as shown in FIG. 1, but are not particularly limited. It may be combined with any circuit as long as the circuit configuration needs to cope with the excessive absorption current.

  FIG. 7 shows a circuit diagram as an example corresponding to the block diagram of FIG.

  An output current from a current detection circuit (not shown; for example, the configuration shown in FIG. 2 is acceptable) is received by a transistor M3 (diode-connected as in FIG. 2), and this is a transistor M4 that forms a current mirror circuit. To absorb current.

  The source of the transistor M4 is grounded, and the drain is connected to the input line from the photoelectric conversion circuit to the electric signal amplification circuit (Amp circuit) via the resistors R1 and R3 connected in series, and is detected by the current detection circuit. The absorption current flows with the generated current.

  Of the resistors R1 and R3, the transistor R5 'closer to the transistor M4 is connected to the transistor M5 in parallel.

  Corresponding to the block of FIG. 6, the resistors R1 and R3 'and the transistor M5 are signal blocking circuits, and the transistors M3 and M4 are current absorption circuits.

  The current absorption circuit is also described in order to describe a specific example of the signal inhibition amount control circuit. However, the circuit configuration other than the signal inhibition amount control circuit is not limited to this circuit. For example, the resistor R1 can be composed of an inductor.

  Next, the signal inhibition amount control circuit will be described. It is the part shown in the dotted-line frame of FIG.

  The transistor M10 and the constant current source I10 connected thereto constitute a voltage detection circuit. One end of the resistor R3 'on the transistor M4 side is connected to the gate (control terminal) of the transistor M10 so as to detect the voltage at the output terminal of the signal blocking circuit. The source of the transistor M10 is connected to the power supply voltage Vcc via the constant current source I10, and the drain is grounded (GND).

  The reference voltage generating circuit includes a transistor M15, a resistor R10, and constant current sources I12 and I13 connected to each of them. One end of the constant current source I12 is connected to Vcc, the other end is connected to the source of the transistor M15, and the drain of the transistor M15 is grounded. The gate of the transistor M15 is grounded via the resistor R10. The resistor R10 is connected to a constant current source I13 having one end connected to Vcc.

  Next is a comparison circuit.

  A transistor M12 having a gate connected to the source of the transistor M10 and a transistor M14 having a gate connected to the source of the transistor M15 are connected to each other in common and grounded via the constant current source I11.

  Vcc is supplied to the drain of the transistor M12 through the diode-connected transistor M11. Further, Vcc is supplied to the drain of the transistor M14 through the transistor M13 which is also diode-connected.

  The transistor M11 that forms a current mirror circuit with the transistor M11 has a gate connected to the drain of the transistor M12, a source supplied with Vcc, and a drain connected to the drain of a transistor M17 described later.

The transistor M13, which forms a current mirror circuit with the transistor M13, has a gate connected to the drain of the transistor M14, a source supplied with Vcc, and a drain connected to the drain of a transistor M19 described later.

  Next, a control signal generation circuit.

  The transistor M17 is diode-connected and forms a current mirror circuit with the transistor M19. That is, the gate of the transistor M17 is connected to the drain of the transistor M17, and the source of the transistor M17 is grounded. The drain of the transistor M17 is supplied with Vcc through the transistor M16.

  The gate of the transistor M19 is connected to the gate of the transistor M17, the source of the transistor M19 is grounded, and Vcc is supplied to the drain via the transistor M18.

  A signal obtained from the drain of the transistor M19 is supplied as a control signal to the signal blocking circuit. That is, the gate of the transistor M5 is connected to the drain of the transistor M19.

  Next, circuit operation will be described.

  The voltage at the output terminal of the signal blocking circuit is input to the gate of the transistor M10, and the corresponding voltage is input to the gate of the transistor M12. On the other hand, a voltage generated in the resistor R10 is input to the gate of the transistor M15, and a voltage corresponding to the voltage is input to the gate of the transistor M14.

  The gate voltages of the transistors M16 and M18 change according to the voltages input to the transistors M12 and M14.

  The voltage input to the gate of the transistor M10 corresponds to the voltage at the output terminal of the signal blocking circuit. The voltage to be compared is the voltage input to the gate of the transistor M15, and is the voltage generated by the resistor R10. This is the reference voltage.

  A voltage corresponding to the voltage of the signal blocking circuit is input to the transistor M12. A voltage corresponding to the reference voltage is input to the transistor M14.

  Since the sources of the transistors M12 and M14 are connected to the common constant current source I11, the current is distributed according to the input voltage of each transistor.

  For example, consider the case where the voltage of the signal blocking circuit is lower than the reference voltage. Since the gate voltage of the transistor M14 is higher than the gate voltage of the transistor M12, more current is distributed to the transistor M14. As a result, the gate voltage of the transistor M16 becomes the gate voltage of the transistor M18. Compared to higher.

  On the other hand, when the voltage of the signal blocking circuit is higher than the reference voltage, the gate voltage of the transistor M14 is lower than the gate voltage of the transistor M12, so that more current is distributed to the transistor M12. As a result, the gate voltage of the transistor M16 is lower than the gate voltage of the transistor M18.

Therefore, when the voltage of the signal blocking circuit is higher than the reference voltage, the gate voltage of the transistor M18 increases, and when the voltage of the signal blocking circuit is lower than the reference voltage, the gate voltage of the transistor M18 decreases.

  Thereby, the control signal (gate voltage) of the transistor M5 guided from the drain of the transistor M19 is low when the voltage of the signal blocking circuit is higher than the reference voltage, and is high when the voltage of the signal blocking circuit is lower than the reference voltage.

  When the DC current absorbed in this way is large, the gate potential of M10 is lowered, the gate potential of M18 is lowered, the drain potential of M19 is raised, and M5 is turned ON. On the other hand, when the DC current is small, the gate potential of M10 is increased, the gate potential of M18 is increased, the drain potential of M19 is decreased, and M5 is turned OFF.

  Thus, a closed loop of negative feedback is formed by the signal blocking circuit and the signal blocking amount control circuit, and the output terminal voltage of the signal blocking circuit, that is, the voltage applied to the current absorption circuit is automatically kept constant. Will be able to.

  Since there is no resistance on the line from which the control signal is extracted, this control signal can be changed in almost full range from Vcc to GND. Since the output terminal resistance of the signal blocking circuit changes according to the amount of current absorption, the present circuit configuration in which the change width of the control signal can be large has an effect that a wide dynamic range of the current absorption amount can be secured.

  In the above embodiment, an example of an optical receiver has been described. However, the above-described DC offset adjustment circuit can also be applied to a wireless device. FIG. 8 shows a block diagram of the radio.

  FIG. 8 shows an embodiment of a direct conversion radio. The received signal from the antenna is subjected to a high-frequency signal processing unit (multiplication with a local signal and down-converted to a baseband signal), and a baseband signal processing unit (signal amplification) that processes the signal from the high-frequency signal processing unit Etc. are performed). The output from the baseband signal processing unit is processed by a digital signal processing unit (not shown). The output from the high-frequency signal processing unit includes a DC offset. Therefore, a signal blocking circuit / current absorption circuit / signal blocking amount control circuit as shown in FIG. 6 is interposed between the high-frequency signal processing unit and the baseband signal processing unit.

  Here, the signal input circuit in FIG. 6 corresponds to the high-frequency signal processing circuit, and the signal amplification circuit corresponds to the baseband signal processing circuit.

  According to the radio apparatus having such a configuration, the dynamic range of DC offset current absorption is wide, and there is an effect that a large adjustment range of DC offset can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  Moreover, although the example using FET as a transistor was shown in the above-mentioned embodiment, it cannot be overemphasized that a transistor may be another kind, for example, a bipolar transistor.

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Explanation of symbols

Electric signal amplification integrated circuit ... 10; photoelectric conversion circuit ... 20; current detection circuit ... 101; electric signal amplification circuit ... 102; current absorption circuit ... 103; signal blocking circuit ... 104

Claims (16)

A photoelectric conversion element;
In an optical signal receiving device including an electric signal amplification integrated circuit that supplies a power supply voltage to the photoelectric conversion element and processes an output signal from the photoelectric conversion element.
The electric signal amplification integrated circuit includes:
A current detection circuit including a first current mirror circuit that detects a current amount flowing into the photoelectric conversion element and outputs a first output current corresponding to the detected current amount;
An electric signal amplifying circuit for amplifying an output signal of the photoelectric conversion element;
DC comprising a second current mirror circuit that turns back a second output current corresponding to the first output current, and absorbing the second output current from an output signal of the photoelectric conversion element input to the amplifier circuit A current absorption circuit;
An optical signal receiving apparatus comprising: It is arranged between the DC current absorption circuit and the input terminal of the electric signal amplification circuit, and is distributed to the DC current absorption circuit and the amplifier by changing its impedance according to the second output current amount. 2. The optical signal receiving apparatus according to claim 1, further comprising a signal blocking circuit for controlling a signal current ratio. 3. The optical signal receiving apparatus according to claim 2, wherein the impedance is changed in accordance with a voltage of the signal blocking circuit. 4. The light according to claim 3, wherein the signal blocking circuit includes a resistor and a transistor connected in parallel to the resistor, and changes a bias voltage of the transistor according to an output terminal voltage of the signal blocking circuit. Signal receiving device. A photoelectric conversion element;
In an optical signal receiving device including an electric signal amplification integrated circuit that supplies a power supply voltage to the photoelectric conversion element and processes an output signal from the photoelectric conversion element.
The electric signal amplification integrated circuit includes:
An electric signal amplifying circuit for amplifying an output signal of the photoelectric conversion element;
A DC current absorption circuit that absorbs a DC current from an output signal of the photoelectric conversion element input to the amplifier circuit;
An optical signal receiving apparatus comprising: a signal blocking circuit in which a blocking amount of a signal current flowing into the DC current absorption circuit from the output signal input to the amplifier circuit is variably set. 6. The signal blocking circuit controls a blocking amount of a signal current flowing from the output signal into the DC current absorption circuit by changing an impedance thereof according to the DC current amount. Optical signal receiver. The signal blocking circuit includes a resistor and a transistor connected in parallel to the resistor, and the bias voltage applied to the transistor is changed according to the signal power of the output signal or the amount of the DC current. 7. The optical signal receiving apparatus according to claim 6, wherein a blocking amount of a signal current flowing into the DC current absorption circuit is controlled. The control is performed such that the impedance is lowered when the potential of the output terminal of the signal blocking circuit is higher than a reference potential, and the impedance is increased when the potential of the output terminal of the signal blocking circuit is lower than the reference potential. 6. The optical signal receiving device according to 6. In an optical signal receiving device comprising a photoelectric conversion element and an electric signal amplification integrated circuit for processing an output signal from the photoelectric conversion element,
The electric signal amplification integrated circuit includes:
An electric signal amplifying circuit for amplifying an output signal of the photoelectric conversion element;
A DC current absorption circuit that absorbs a DC current from an output signal of the photoelectric conversion element input to the amplifier circuit;
A signal blocking circuit which is interposed between the input terminal of the amplifier circuit and the DC current absorption circuit and in which the blocking amount of the signal current flowing from the output signal into the DC current absorption circuit is variably set;
A signal blocking amount control circuit for controlling a signal blocking amount of the signal blocking circuit,
The signal blocking amount control circuit includes:
A voltage detection circuit for detecting a voltage at an output terminal of the signal blocking circuit;
A comparison circuit that compares a voltage at the output terminal of the signal blocking circuit detected by the signal blocking circuit with a reference voltage;
An optical signal receiving device comprising: a control signal generating circuit that generates a control signal for controlling a signal blocking amount of the signal blocking circuit based on a comparison result in the comparing circuit. 10. The optical signal receiving apparatus according to claim 9, wherein the signal blocking circuit includes a resistor and a transistor connected in parallel to the resistor, and the control signal controls a bias voltage of the transistor. A photoelectric conversion element;
In an optical signal receiving device including an electric signal amplification integrated circuit that supplies a power supply voltage to the photoelectric conversion element and processes an output signal from the photoelectric conversion element,
The electric signal amplification integrated circuit includes:
A current detection circuit including a first current mirror circuit that detects a current amount flowing into the photoelectric conversion element and outputs a first output current corresponding to the detected current amount;
An electric signal amplifying circuit for amplifying an output signal of the photoelectric conversion element;
DC comprising a second current mirror circuit that turns back a second output current corresponding to the first output current, and absorbing the second output current from an output signal of the photoelectric conversion element input to the amplifier circuit A current absorption circuit;
A signal blocking circuit which is interposed between the input terminal of the amplifier circuit and the DC current absorption circuit and in which the blocking amount of the signal current flowing from the output signal into the DC current absorption circuit is variably set;
A signal blocking amount control circuit for controlling a signal blocking amount of the signal blocking circuit,
The signal blocking amount control circuit includes:
A voltage detection circuit for detecting a voltage at an output terminal of the signal blocking circuit;
A comparison circuit that compares a voltage at the output terminal of the signal blocking circuit detected by the signal blocking circuit with a reference voltage;
An optical signal receiving apparatus comprising: a control signal generating circuit that generates a control signal for controlling a signal blocking amount of the signal blocking circuit based on a comparison result in the comparing circuit. 12. The signal blocking circuit controls a blocking amount of a signal current flowing from the output signal into the DC current absorption circuit by changing an impedance thereof according to the DC current amount. Optical signal receiver. The signal blocking circuit includes a resistor and a transistor connected in parallel to the resistor, and by changing a bias voltage applied to the transistor, a blocking amount of a signal current flowing from the output signal into the DC current absorption circuit. 12. The optical signal receiving apparatus according to claim 11, wherein the optical signal receiving apparatus is controlled. An electrical signal amplifier circuit for amplifying a signal including a DC offset current;
A DC current absorption circuit for absorbing the DC offset current from the signal;
A signal blocking circuit interposed between the input terminal of the amplifier circuit and the DC current absorption circuit, wherein the blocking amount of the signal current flowing from the signal into the DC current absorption circuit is variably set;
A signal blocking amount control circuit for controlling a signal blocking amount of the signal blocking circuit,
The signal blocking amount control circuit includes:
A voltage detection circuit for detecting a voltage at an output terminal of the signal blocking circuit;
A comparison circuit that compares a voltage at the output terminal of the signal blocking circuit detected by the signal blocking circuit with a reference voltage;
A DC offset adjustment circuit, comprising: a control signal generation circuit that generates a control signal for controlling a signal blocking amount of the signal blocking circuit based on a comparison result in the comparison circuit. 15. The signal blocking circuit controls a blocking amount of a signal current flowing from the output signal into the DC current absorption circuit by changing an impedance thereof according to the DC offset current amount. DC offset adjustment circuit. The signal blocking circuit includes a resistor and a transistor connected in parallel to the resistor, and by changing a bias voltage applied to the transistor, a blocking amount of a signal current flowing from the output signal into the DC current absorption circuit. The DC offset adjustment circuit according to claim 14, wherein:

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