JPH1175226A - Subscriber circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize an operational amplifier which is usable for three systems in common and has high dielectric strength and a wide band by dividing a signal processing part into a signal output part for outputting a transmit signal and a bias voltage supply part, and composing the signal output part of a low- dielectric-strength, wide-band amplifier part and the bias part of a high- dielectric-strength, narrow-band amplifier part. SOLUTION: The bias part 30 receives the outputs of amplifiers 3 and 4 and applies a DC bias to the transmit signal and is composed of the high- dielectric-strength, narrow-band amplifier part. The signal output part 40 receives the output of the bias part 30 and sends the transmit signal to lines A and B and is equipped with a low-dielectric-strength, high-band operational amplifier, and its phase compensation is controlled by a switching control part 20. The switching control part 20 controls the disconnection and connection of a feedback circuit 2A and switches the phase compensation of the signal output part 40. Consequently, the circuit can be used for the analog system, 2B1Q system, and ping-pong system in common.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a subscriber circuit,
More specifically, the present invention relates to a subscriber circuit that can be shared by the analog system, the 2B1Q system, and the ping-pong system.

[0002]

2. Description of the Related Art Conventionally, a subscriber circuit is different from an analog subscriber circuit for transmitting voice and a basic rate subscriber circuit (2B1Q system, ping-pong system) for transmitting digital signals. Has been realized. The digital system has twice the amount of information and uses different signal codes and signal voltages as compared with the analog system, and thus has conventionally been realized by different circuits.

FIG. 5 is a comparative explanatory diagram of each subscriber system.
The comparison is made for each of the signal code, the signal speed, the signal amplitude, and the termination. For example, while the signal speed of the analog system is 300 to 3400 Hz, the 2B1Q system is 160 kbps and the ping-pong system is 320 kbps. The signal amplitude is 1.55 V for the analog method.
_OP (V _OP indicates a voltage from 0 to a peak value; the same applies hereinafter), whereas the 2B1Q method is 2.5 V _OP and the ping-pong method is 6 V _OP . The termination resistance is about 600Ω for the analog method, about 135Ω for the 2B1Q method, and about 110Ω for the ping-pong method.

Therefore, when a subscriber desires to change from an analog system to a digital system (2B1Q or ping-pong), the corresponding circuit printed circuit board (PCB: Principle) is manually operated.
tCircuit Board) had to be replaced. Therefore, in a system or the like that is installed at a distance from the switching center, such as a remote facility, the replacement of the PCB requires the work of a maintenance person, and the replacement is time-consuming and uneconomical. Therefore, it is required to realize both functions on the same PCB.

FIG. 6 is a diagram showing a configuration example of a conventional analog subscriber circuit. In the figure, reference numeral 1 denotes a codec (CODEC) for converting an audio signal. Codec 1
Is connected to the subscriber circuit side, and the other is connected to the highway (HW) side. On the highway side, a data input terminal (D-IN) and a data output terminal (D-OU)
T) is provided and connected to the highway.

[0006] The digital audio signal is converted into an analog signal in the codec, and is converted to an analog output terminal (A-OU).
T). On the other hand, the received signal enters the analog input terminal (A-IN) terminal. 2 is an analog input terminal A-
It is a feedback circuit connected between IN and the analog output terminal A-OUT. The feedback circuit 2 is specifically composed of an internal termination resistor 2a.

Reference numerals 3 and 4 denote amplifiers that receive and amplify the analog output of the codec 1. 4 is an inverting amplifier. 5
Is a bias voltage supply unit which receives outputs of the amplifiers 3 and 4 and applies a bias voltage, and is constituted by a bias circuit 5a. The power supply voltage V _BB (−
48V).

Reference numeral 6 denotes a signal output unit that receives an output of the bias voltage supply unit 5 and outputs an audio signal. The signal output unit 6
Is composed of amplifiers AP1 and AP2 constituting a buffer amplifier. An operational amplifier is used for each of the amplifiers AP1 and AP2. Reference numeral 7 denotes a phase compensation circuit 7 for compensating the phase of these amplifiers, and uses a capacitor C1.

The output of the amplifier AP1 is connected to the line A via an external terminating resistor R, and the output of the amplifier AP2 is connected to the line B via an external terminating resistor R. A telephone (not shown) is connected between the A line and the B line. Reference numeral 8 denotes a signal receiving unit that receives audio signals from the A-line and the B-line, and includes, for example, a differential amplifier AP3. The differential amplifier is composed of an operational amplifier, and the output of the signal receiving unit AP3 is connected to the analog input terminal A-IN of the codec 1. The operation of the circuit thus configured will be described as follows.

[0010] This analog subscriber circuit usually has a voltage of -48V.
And a maximum of 3.17 dBm0 (zero relative level) and an analog signal of 300 Hz to 3400 Hz are superimposed on the subscriber line (A line, B line) as a differential signal. The zero relative level indicates the level converted to the point when the level of the reference point is set to 0. For example, in the case of an impedance line of 600Ω, the level for supplying 1 mW to the impedance line of 0dBm0 = 600Ω ≒ 0.775 (V).

The transmission signal is output from the analog output terminal (A-OUT) of the codec 1, amplified by the amplifiers 3 and 4, and then superimposed on the bias voltage by the subsequent bias voltage supply unit 5. The outputs of the respective bias circuits are output from the signal output amplifiers AP1 and AP2 to the subscriber's A and B lines as differential analog signals.

On the other hand, the received signal is input to the differential amplifier AP3 of the signal receiving unit 8, connected to the internal terminating resistor 2a, and input to the analog input terminal (A-IN) of the codec 1. The received signal is fed back to the signal output unit via the feedback circuit 2 to terminate the two wires.

As described above, in the analog subscriber circuit, since the feedback system is formed and terminated via several amplifiers, the operational amplifiers AP1 and AP2 for preventing oscillation are provided.
Is provided with a phase compensation circuit 7 for performing sufficient phase compensation.

FIG. 7 is a diagram showing a configuration example of an operational amplifier. Since the analog subscriber circuit is fed back, a phase compensation circuit 7 is provided so that the circuit does not oscillate. FIG. 8 is a diagram illustrating an example of gain-frequency characteristics of an operational amplifier used in a subscriber circuit. The vertical axis represents the gain (dB), and the horizontal axis represents the frequency (Hz). FIG. 8 is generally called a Bode diagram.

F1 is an open-loop characteristic of the amplifier, which is a characteristic when phase compensation is not performed, and is a characteristic used in the case of the ping-pong system. The characteristics of f1 are 6dB / oct and 12dB
The / oct stage is created. With a slope of 12 dB / oct, the output phase deviates from the input by 180 degrees, becomes positive feedback even when negative feedback is applied, and oscillates in the feedback circuit as it is.

F2 is a characteristic obtained by lowering the frequency characteristic by slightly compensating the phase, and is used in the case of the 2B1Q system. f3 is a characteristic used in the analog system in which the frequency characteristic is lowered by applying sufficient phase compensation so that the circuit does not oscillate even when feedback is applied. The slope of the characteristic f3 is 6 dB / oct.

The external terminating resistor R of the subscriber line in FIG.
Is a resistance for protection of, for example, 50Ω, for example, 600
When realizing Ω termination, the feedback circuit
The remaining 500Ω (= 600−50 × 2) is realized.

FIG. 9 is a diagram showing a configuration example of a conventional 2B1Q subscriber circuit. 6 are denoted by the same reference numerals. The 2B1Q method has four values (+3, -3,
This is a system using digital signals of (+1, -1). Therefore, in terms of frequency spectrum, 40 kHz to 80 kHz
Hz band is required.

In the figure, reference numeral 9 denotes an interface (INF) provided between a subscriber circuit and a highway (HW).
, 3 and 4 are amplifiers for amplifying output signals, 6 is a signal output unit for receiving the outputs of the amplifiers 3 and 4, and an operational amplifier AP1
And AP2. C2 is a capacitor constituting the phase compensation circuit 7. The values of these capacitors C2 are smaller than those of the capacitors C1 in the analog subscriber circuit shown in FIG.

T1 is a transformer whose secondary side is connected between operational amplifiers AP1 and AP2. The primary winding of the transformer T1 is connected to the A line and the B line. A power supply circuit 10 supplies a DC power supply current to the transformer T1. C is a capacitor connected to the secondary side of the transformer T1, and the position of the capacitor C is the middle point of the primary side. Reference numeral 8 denotes a signal receiving unit that receives a reception signal, and the output is input to the interface unit 9. The signal receiving section 8 includes a differential amplifier A
P3. The operation of the circuit thus configured will be described as follows.

The transmission signal passes through the interface unit 9 and is converted into a differential signal at the signal output unit 6, and is output to the subscriber lines A and B via the transformer T1. The DC component supplied from the power supply circuit 10 from the position of the capacitor C is superimposed on the transmission signal.

On the other hand, the received signal enters the operational amplifier AP3 of the signal receiving section 8 from the subscriber line via the transformer T1.
The data is input to the interface unit 9. Termination is transformer T
1 is determined from the winding resistance, the winding ratio, and the resistance value of the resistor R. Therefore, there is no internal termination by a feedback circuit such as an analog subscriber circuit. In order to prevent the signal output unit 6 from oscillating, the operational amplifiers AP1 and AP2 of the signal output unit 6 are provided with a phase compensation circuit 7 having a characteristic indicated by f2 in FIG.

FIG. 10 is a diagram showing a configuration example of a conventional ping-pong subscriber circuit. The same components as those in FIG. 9 are denoted by the same reference numerals. The ping-pong method is a method in which transmission and reception are alternately repeated. 6V _OP , 160 kbps signal is transmitted and received on the transmission / reception side in a time division manner.
This is a method of transmitting and receiving a high-speed AMI signal equivalent to 20 kbps in a time-division manner.

Referring to FIG. 1, reference numeral 11 denotes an interface / control unit for performing signal interface and control. Reference numerals 3 and 4 denote amplifiers for amplifying transmission signals, AP1 and AP
An operational amplifier 2 receives the outputs of the amplifiers 3 and 4.
The signal output unit 6 is composed of the operational amplifiers AP1 and AP2, but the operational amplifier is not phase-compensated as compared with the analog system and the 2B1Q system.

T2 is a transformer whose secondary side is connected between operational amplifiers AP1 and AP2. The A line and the B line are connected to the primary side of the transformer T2. Transformer T
On the primary side of 2, the DC component is supplied from the power supply circuit 10 after the DC component is cut by the capacitor C.

Reference numeral 12 denotes a signal reception switching unit that supplies the secondary side of the transformer T2 to the signal reception unit 8 when receiving a signal.
The switch contact of the signal reception switching unit 12 is supplied with a control signal from the interface / control unit 11 so as to be turned off when transmitting a signal and turned on only when receiving a signal. The operation of the circuit thus configured will be described as follows.

This circuit connects the received signal to the signal receiving unit 8 by the signal receiving switching unit 12 when receiving the signal, and disconnects the signal receiving unit 8 when transmitting the signal.
Alternatively, at the time of transmission, the receiving unit does not accept the signal.

The transmission signal passes through the output terminal OUT of the interface / control unit 11 and is superimposed on the DC component supplied from the power supply circuit 10 via the transformer T2 as a differential signal at the signal output unit 6, Subscriber line (line A,
B).

The received signal passes through the signal reception switching unit 12 from the subscriber line via the transformer T2, and passes through the signal reception unit 8
And enters the input terminal IN of the interface / control unit 11 from the amplifier AP3.

The termination is determined by the winding resistance of the transformer T2, the turns ratio, and the resistance value of the resistor R. In this circuit, since there is no feedback, the operational amplifiers AP1 and AP2 of the signal output unit 6 do not need a phase compensation circuit in particular, and need to receive a signal faster than the 2B1Q system. Not.

[0031]

The above three systems have fundamentally different circuits depending on the difference in the frequency of the output signal and the type of termination used. The first problem is due to the difference in the phase compensation band used by the operational amplifier. In the analog circuit system, sufficient phase compensation is required, and in the 2B1Q system, the phase compensation is minimized because of a wider band than the analog circuit system. In the ping-pong system, a phase compensation circuit cannot be provided because of a higher speed. Therefore, it has been difficult to realize the three methods simultaneously.

The second problem is how to speed up the operational amplifier itself. Phase compensation originally limits the characteristics of a wide band, and even in the 2B1Q system, the characteristics before phase compensation need to be sufficiently wide.

Here, an operational amplifier which operates at a voltage as high as 48 V of an analog circuit is required. The transistor elements constituting these operational amplifiers have a high breakdown voltage and a large size. For large transistor elements,
Generally, since the parasitic capacitance (C _ob ) itself is large, it is not suitable for high frequency (broad band).

When operating at a high frequency, there are the following problems. You need a small device. This indicates that only transistors with a low breakdown voltage can be used. It is necessary to supply extra current. This indicates that power consumption is not reduced.

Therefore, in the conventional method, it is difficult to produce an operational amplifier having a high withstand voltage and a wide band. The present invention has been made in view of such a problem, and the first invention
Secondly, it is an object of the present invention to provide a subscriber circuit which can be used commonly for the above three methods, and which can realize a high-voltage and wide-band operational amplifier.

[0036]

[Means for Solving the Problems]

(1) FIG. 1 is a principle block diagram of the present invention. 6 are denoted by the same reference numerals. The circuit shown in the figure is a subscriber circuit capable of realizing the analog system, 2B1Q, or ping-pong system.

In the figure, reference numeral 30 denotes a switching control unit for performing transmission and reception of signals and switching control of switches provided in each unit of the subscriber circuit. The switching control unit 20 includes:
One is connected to a highway (HW) and the other is connected to a subscriber circuit. 2A is a feedback circuit connected between the output terminal A-OUT and the input terminal A-IN of the switching control unit 30. The feedback circuit 2A has a switch unit for disconnecting the circuit inside the feedback circuit 2A. The circuit can be disconnected or connected by the switching signal.

Reference numeral 3 denotes an amplifier for amplifying the transmission signal from the switching control unit 20, and reference numeral 4 denotes an amplifier for inverting and amplifying the transmission signal from the switching control unit 20. Reference numeral 30 denotes a bias unit that receives the outputs of the amplifiers 3 and 4 and applies a DC bias to the transmission signal. The bias unit 30 has a high withstand voltage,
It consists of a narrow band amplifier.

Reference numeral 40 denotes an output from the bias unit 30 and A
A signal output unit that outputs a transmission signal to the line and the B line. The signal output unit 40 includes two low-voltage, wide-band operational amplifiers for the A line and the B line therein, and the phase compensation thereof can be changed by a switching signal from the switching control unit 20. I can do it. Specifically, the capacity of the capacitor for phase compensation is changed. The bias processing unit 30 and the signal output unit 40 constitute a signal processing unit. That is, the signal processing unit is divided into the bias unit 30 and the signal output unit 40.

Reference numeral 8 denotes a signal receiving unit for receiving signals from the A line and the B line. The output is input to the A-IN terminal of the switching control unit 20. According to the configuration of the present invention, the switching control unit 20 controls the disconnection and connection of the feedback circuit 2A, and switches the phase compensation of the signal output unit 40, so that the analog system, the 2B1Q system, and the ping-pong system are switched. Can be provided with a subscriber circuit that can be used in common.

Further, the signal output section 40 for signal output and the bias section 30 for supplying a bias voltage are divided, and the operational amplifier constituting the signal output section 40 is configured with a low withstand voltage and wide band, and the bias section 30 is formed. By configuring the amplifier with a high withstand voltage and narrow band amplifier section, it is possible to provide a subscriber circuit capable of realizing a high withstand voltage and wide band operational amplifier.

(2) In this case, the phase compensation circuit of the amplifier section of the signal output section 40 is switched or separated. According to the configuration of the present invention, the subscriber circuit can be shared by the analog system, the 2B1Q system, and the ping-pong system by switching or disconnecting the phase compensation circuit of the amplifier unit of the signal output unit 40.

(3) The feedback circuit from the signal receiving unit 8 for receiving the received signal to the signal output unit 40 is connected in the case of the analog system, and is disconnected in the case of the 2B1Q system or the ping-pong system. It is characterized by.

According to the configuration of the present invention, the feedback circuit from the signal receiving unit 8 to the signal output unit 40 is connected in the case of the analog system, and is disconnected in the case of the 2B1Q system or the ping-pong system, thereby providing the subscriber circuit. Can be shared by the analog system, the 2B1Q system, and the ping-pong system.

(4) Further, the present invention is characterized in that the external terminating resistor is switched between the analog system, the 2B1Q system, and the ping-pong system. According to the configuration of the present invention, by switching the external terminating resistor in each method, the termination most suitable for each method can be performed.

(5) The external termination resistor is set to an intermediate value between the ping-pong system and the 2B1Q system, and switching between this resistor and the analog termination resistor is controlled.

According to the configuration of the present invention, the external terminating resistor can be shared between the 2B1Q system and the ping-pong system. (6) Further, a common mode choke coil is inserted between the A line and the B line.

According to the structure of the present invention, the common mode choke coil is inserted between the A line and the B line, so that the A
It is possible to suppress distortion from the differential signal due to the difference between the positive and negative slew rates caused by speeding up the line side operational amplifier and the B line side operational amplifier.

[0049]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1 and 6 are denoted by the same reference numerals. In the figure, reference numeral 20a denotes a switching unit for switching the internal signal processing circuit according to the analog, 2B1Q, ping-pong method, and 20b denotes a control unit for supplying a switching signal according to the analog, 2B1Q, ping-pong method to each circuit. The switching unit 20a outputs a transmission signal from the output terminal A-OUT, and outputs the transmission signal from the input terminal AI.
Input the received signal to N. The switching section 20a and the control section 20b constitute the switching control section 20 of FIG.

2a is an input terminal AI of the switching section 20a.
N and an internal terminal connected between the output terminal A-OUT and 2
Reference numeral b denotes a feedback disconnection circuit that is connected in series with the internal termination 2a and disconnects and connects the feedback circuit. The internal termination section 2a and the feedback disconnection circuit 2b constitute the feedback circuit 2A of FIG.

Reference numeral 3 denotes an amplifier for amplifying the transmission signal, and reference numeral 4 denotes an amplifier for inverting and amplifying the transmission signal. Reference numeral 30 denotes a bias unit that receives the outputs of the amplifiers 3 and 4. The bias unit 30 includes a first power supply (AP1 power supply) 31 receiving the output of the amplifier 3 and a second power supply (AP1) receiving the output of the amplifier 4.
(Two power supplies) 32.

Reference numeral 40 denotes a first operational amplifier AP1 which receives an output of the amplifier 3 and outputs a signal to the A line, and a second operational amplifier AP2 which receives an output of the amplifier 4 and outputs a signal to the B line.
And a phase compensation circuit 7A for the amplifiers AP1 and AP2. The output of the amplifier 3 is input to the input of the operational amplifier AP1, and the output of the amplifier 4 is input to the input of the operational amplifier AP2. Also, the AP1 power supply 3
1 is the operating voltage of the operational amplifier AP1, and
The output of the P2 power supply 32 is the operating voltage of the operational amplifier AP2.

In the operational amplifier AP1, one of the phase compensation terminals coming out of AP1 has a phase compensation capacitor C
1 and C2 are commonly connected, and changeover switches SW1 and SW2 are connected to the other terminal. First, the switch SW2 selects one of the capacitors C1 and C2, and the switch SW1 determines whether or not to connect the other end of one of the capacitors selected by the switch SW2 to the other phase compensation terminal of the amplifier AP1. Switch.

In the operational amplifier AP2, one of the phase compensation terminals coming out of AP2 is connected to a phase compensation capacitor C.
1 and C2 are commonly connected, and changeover switches SW3 and SW4 are connected to the other terminal. First, the switch SW4 selects one of the capacitors C1 and C2, and the switch SW3 determines whether or not to connect the other end of one of the capacitors selected by the switch SW4 to the other phase compensation terminal of the amplifier AP2. Switch.

Reference numeral 50 denotes an external terminal for receiving the outputs of the operational amplifiers AP1 and AP2. The external termination 50 is connected to a resistor R
1 and R2, and switches SW5 and SW6 for selecting one of these resistors. The outputs of the operational amplifiers AP1 and AP2 are
The resistors R1 and R2 are connected to the A and B lines, respectively, as external terminating resistors. Here, R1 is for the analog system, R2 is for 2B1Q, ping-pong system.

As shown in FIG. 5, strictly speaking, 2B1
The terminating resistance in the case of the Q method is slightly different from 135Ω, and the terminating resistance in the case of the ping-pong method is slightly different from 110Ω. Therefore, if the external terminating resistor R2 is, for example, 123Ω which is intermediate between the 2B1Q system and the ping-pong system, an error is slightly generated in each case, but the external terminating resistor can be shared.

Reference numeral 8 denotes a signal receiving section for receiving signals received from the A and B lines, for example, a differential amplifier is used. The output of the signal receiving unit 8 is connected to the input terminal A-IN of the switching unit 20a. The operation of the circuit thus configured will be described as follows.

The control unit 20b switches the input / output signal system between the input terminal A-IN and the output terminal A-OUT of the switching unit 20a, disconnects the feedback path, disconnects the internal termination resistor, and disconnects the external termination unit. The switching and the switching of the phase compensation circuit are performed.

In the case of operating as an analog subscriber circuit In this case, the control unit 20b supplies a control signal to the switching unit 20a, and changes the input / output signal system of the input terminal A-IN and the output terminal A-OUT to the analog system. So that Then, a control signal is given to the feedback separation circuit 2b, and the internal termination 2a is connected to the feedback circuit.
Then, the switches SW5 and SW connected to the A line and the B line
A switching signal is given to 6 and the external terminating resistor is set to R1. As a result, a total termination of 600Ω is realized in combination with the external terminating resistor R1 and the internal terminating resistor.

The operational amplifier AP1 of the signal output unit 40
And the phase compensation circuit of AP2 are set as follows. That is, in the operational amplifier AP1, the switch SW1 connects the phase compensation circuit 7A to the phase compensation terminal, and sets the switch SW2 to the capacitor C1 side. Next, in the operational amplifier AP2, the switch SW3 connects the phase compensation circuit 7A to the phase compensation terminal, and sets the switch SW4 to the capacitor C1 side. Thereby, the operational amplifier AP
Sufficient phase compensation is performed for 1 and AP2, and the characteristics are as shown by f3 in FIG.

The bias section 30 and the signal output section 40 are separated, and the bias section 30 is connected to the AP1 power supply 31.
And the AP2 power supply 32 is used as a power supply voltage for the operational amplifiers AP1 and AP2, and a power supply voltage is provided so that the operational amplifiers AP1 and AP2 can operate with a low breakdown voltage and a wide band.

FIG. 3 is a diagram showing the relationship between the power supplies for AP1 and AP2 and the operational amplifier following the power supply. AP1 power supply is -4
The operating range is set near eight power supplies, and a signal voltage as shown by the waveform in the figure is applied to the operational amplifier. Also, AP
The operating range of the two power supplies is set near 0 V, and a signal voltage as shown by the waveform in the figure is applied to the operational amplifier.

In the case of operating as a 2B1Q subscriber circuit In this case, the control unit 20b supplies a control signal to the switching unit 20a, and changes the input / output signal system of the input terminal A-IN and the output terminal A-OUT to the 2B1Q system. So that Then, a control signal is given to the feedback disconnection circuit 2b to disconnect the internal termination 2a. As a result, the feedback circuit is eliminated, and the circuit becomes an open loop.
Then, the switches SW5 and SW connected to the A line and the B line
6 and a switching signal is given to set the external terminating resistor to R2. At this time, the resistance value of the external terminating resistor R2 is １ ／ of the terminating resistance value. As a result, the termination of 123Ω close to 135Ω is performed.

The operational amplifier AP1 of the signal output unit 40
And the phase compensation circuit of AP2 are set as follows. That is, in the operational amplifier AP1, the switch SW1 connects the phase compensation circuit 7A to the phase compensation terminal, and the switch SW2 is set to the capacitor C2 side. Next, in the operational amplifier AP2, the switch SW3 connects the phase compensation circuit 7A to the phase compensation terminal, and sets the switch SW4 to the capacitor C2 side. Thereby, the operational amplifier AP
1 and AP2 are compensated to some extent,
The characteristic is as shown by f2 in FIG.

The bias section 30 is separated from the signal output section 40, and the bias section 30 is connected to the AP1 power supply 31.
And the AP2 power supply 32 is used as a power supply voltage for the operational amplifiers AP1 and AP2, and a power supply voltage is provided so that the operational amplifiers AP1 and AP2 can operate with a low breakdown voltage and a wide band.

In the case of operating as a ping-pong subscriber circuit In this case, the control unit 20b supplies a control signal to the switching unit 20a, and changes the input / output signal system of the input terminal A-IN and the output terminal A-OUT to the ping-pong system. So that Then, a control signal is given to the feedback disconnection circuit 2b to disconnect the internal termination 2a. As a result, the feedback circuit is eliminated, and the circuit becomes an open loop.
Then, the switches SW5 and SW connected to the A line and the B line
6 and a switching signal is given to set the external terminating resistor to R2. At this time, the resistance value of the external terminating resistor R2 is １ ／ of the terminating resistance value. As a result, the termination of 123Ω close to 110Ω is performed.

Then, the control section 20b operates the operational amplifier AP1.
Switch SW to separate the phase compensation circuit between
1 and the switch SW3 are switched to the opposite side. As a result, the phase compensation circuits are connected to the operational amplifiers AP1 and AP1, respectively.
Disconnected from 2. The operational amplifiers AP1 and AP at this time
The characteristic of No. 2 is as shown by f1 in FIG.

The bias unit 30 and the signal output unit 40 are separated, and the bias unit 30
And the AP2 power supply 32 is used as a power supply voltage for the operational amplifiers AP1 and AP2, and a power supply voltage is provided so that the operational amplifiers AP1 and AP2 can operate with a low breakdown voltage and a wide band.

According to the embodiment described above, the switching control section 20 controls the disconnection and connection of the feedback circuit 2A and the switching of the phase compensation of the signal output section 40. 2B1Q
It is possible to provide a subscriber circuit that can be used in common for a circuit of a system and a ping-pong system.

Further, the signal output section 40 for signal output and the bias section 30 for supplying a bias voltage are divided, and the operational amplifier constituting the signal output section 40 is configured with a low withstand voltage and wide band. By configuring the amplifier with a high withstand voltage and narrow band amplifier section, it is possible to provide a subscriber circuit capable of realizing a high withstand voltage and wide band operational amplifier.

Also, by switching or disconnecting the phase compensation circuit in the amplifier section of the signal output section 40,
The subscriber circuit can be shared by the analog system, the 2B1Q system, and the ping-pong system.

Further, the feedback circuit from the signal receiving section 8 to the signal output section 40 is connected in the case of the analog system, and disconnected in the case of 2B1Q or ping-pong system, so that the subscriber circuit is analog system, 2B1Q. method,
It can be shared by the ping-pong method.

Further, by switching the external terminating resistor between the analog system, the 2B1Q system, and the ping-pong system, it is possible to perform the most suitable termination for each system.

Further, the external terminating resistor is provided by a ping-pong system and 2B.
The external termination can be shared between the 2B1Q system and the ping-pong system by setting the intermediate value of the 1Q system and controlling the switching between this resistor and the internal termination resistor of the analog system.

FIG. 4 is a circuit diagram showing another embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals. This embodiment differs from the embodiment shown in FIG. 2 in that the configuration of the bias unit 30 is different and that the common mode choke coil L is provided on the A line and the B line. Other configurations are the same as those in FIG.

In the bias section 30, R3, R4, R
Reference numeral 5 denotes a bias setting resistor connected in series, which is connected to the ground and a -48 V power supply (V _BB ). Resistance R3
The potential at the connection point between R4 and R4 is connected via the operational amplifier 33 to the output side of the operational amplifier AP1 to provide a DC bias potential. Further, the potential at the connection point between the resistors R4 and R5 is connected to the output side of the operational amplifier AP2 via the operational amplifier 34, and gives a DC bias potential. In this embodiment, the outputs of the operational amplifiers AP1 and AP2 are respectively supplied via DC cut capacitors C3. The operation of the circuit thus configured will be described as follows.

In the case of operating as an analog subscriber circuit In this case, the control unit 20b supplies a control signal to the switching unit 20a, and changes the input / output signal system of the input terminal A-IN and the output terminal A-OUT to the analog system. So that Then, a control signal is given to the feedback separation circuit 2b, and the internal termination 2a is connected to the feedback circuit.
Then, the switches SW5 and SW connected to the A line and the B line
A switching signal is given to 6 and the external terminating resistor is set to R1. As a result, a total termination of 600Ω is realized in combination with the external terminating resistor R1 and the internal terminating resistor.

The operational amplifier AP1 of the signal output unit 40
And the phase compensation circuit of AP2 are set as follows. That is, in the operational amplifier AP1, the switch SW1 connects the phase compensation circuit 7A to the phase compensation terminal, and sets the switch SW2 to the capacitor C1 side. Next, in the operational amplifier AP2, the switch SW3 connects the phase compensation circuit 7A to the phase compensation terminal, and sets the switch SW4 to the capacitor C1 side. Thereby, the operational amplifier AP
Sufficient phase compensation is performed for 1 and AP2, and the characteristics are as shown by f3 in FIG.

The bias section 30 and the signal output section 40 are separated from each other. An operational amplifier having a low withstand voltage and a wide band is provided in the signal output section 40, and the bias section 30 for operating the operational amplifier itself has a high voltage bias. The voltage is supplied to the subscriber line, and the signal output unit 40 outputs a signal voltage.

In the case of operating as a 2B1Q subscriber circuit In this case, the control unit 20b supplies a control signal to the switching unit 20a and changes the input / output signal system of the input terminal A-IN and the output terminal A-OUT to the 2B1Q system. So that Then, a control signal is given to the feedback disconnection circuit 2b to disconnect the internal termination 2a. As a result, the feedback circuit is eliminated, and the circuit becomes an open loop.
Then, the switches SW5 and SW connected to the A line and the B line
6 and a switching signal is given to set the external terminating resistor to R2. At this time, the resistance value of the external terminating resistor R2 is １ ／ of the terminating resistance value. As a result, the termination of 123Ω close to 135Ω is performed.

The operational amplifier AP1 of the signal output unit 40
And the phase compensation circuit of AP2 are set as follows. That is, in the operational amplifier AP1, the switch SW1 connects the phase compensation circuit 7A to the phase compensation terminal, and the switch SW2 is set to the capacitor C2 side. Next, in the operational amplifier AP2, the switch SW3 connects the phase compensation circuit 7A to the phase compensation terminal, and sets the switch SW4 to the capacitor C2 side. Thereby, the operational amplifier AP
1 and AP2 are compensated to some extent,
The characteristic is as shown by f2 in FIG.

The bias section 30 and the signal output section 40 are separated from each other. An operational amplifier having a low withstand voltage and a wide band is provided in the signal output section 40, and the bias section 30 for operating the operational amplifier itself is provided with a high voltage bias. The voltage is supplied to the subscriber line, and the signal output unit 40 outputs a signal voltage.

In the case of operating as a ping-pong subscriber circuit In this case, the control unit 20b supplies a control signal to the switching unit 20a, and changes the input / output signal system of the input terminal A-IN and the output terminal A-OUT to the ping-pong system. So that Then, a control signal is given to the feedback disconnection circuit 2b to disconnect the internal termination 2a. As a result, the feedback circuit is eliminated, and the circuit becomes an open loop.

Then, a switching signal is given to the switches SW5 and SW6 connected to the lines A and B, and the external terminating resistor is set to R2. At this time, the resistance value of the external terminating resistor R2 is １ ／ of the terminating resistance value. As a result, the termination of 123Ω close to 110Ω is performed.

Then, the control unit 20b operates the operational amplifier AP1.
Switch SW to separate the phase compensation circuit between
1 and the switch SW3 are switched to the opposite side. As a result, the phase compensation circuits are connected to the operational amplifiers AP1 and AP1, respectively.
Disconnected from 2. The characteristics of the operational amplifiers AP1 and AP2 are as shown by f1 in FIG.

Further, the bias section 30 and the signal output section 40 are separated, and a low withstand voltage, wide band operational amplifier is provided in the signal output section 40, and the bias section 30 for operating the operational amplifier itself is provided with a high voltage bias. The voltage is supplied to the subscriber line, and the signal output unit 40 outputs a signal voltage.

According to the embodiment described above, the switching control section 20 controls the disconnection and connection of the feedback circuit 2A, and the switching of the phase compensation of the signal output section 40. 2B1Q
It is possible to provide a subscriber circuit that can be used in common for a circuit of a system and a ping-pong system.

Further, the signal output section 40 for signal output and the bias section 30 for supplying a bias voltage are divided, and the operational amplifier constituting the signal output section 40 is configured with a low withstand voltage and wide band. By configuring the amplifier with a high withstand voltage and narrow band amplifier section, it is possible to provide a subscriber circuit capable of realizing a high withstand voltage and wide band operational amplifier.

Further, by switching or disconnecting the phase compensation circuit in the amplifier section of the signal output section 40,
The subscriber circuit can be shared by the analog system, the 2B1Q system, and the ping-pong system.

Also, the feedback circuit from the signal receiving section 8 to the signal output section 40 is connected in the case of the analog system and disconnected in the case of the 2B1Q or ping-pong system, so that the subscriber circuit is analog system, 2B1Q. method,
It can be shared by the ping-pong method.

By switching the external terminating resistor between the analog system, the 2B1Q system, and the ping-pong system, it is possible to perform the most suitable termination for each system.

Further, the external terminating resistor is provided by a ping-pong system and 2B.
The external termination can be shared between the 2B1Q system and the ping-pong system by setting the intermediate value of the 1Q system and controlling the switching between this resistor and the internal termination resistor of the analog system.

In this embodiment, a common mode choke coil L is connected between the A line and the B line. According to this, it is possible to suppress the distortion from the differential signal due to the difference between the positive and negative slew rates caused by speeding up the A-line side operational amplifier and the B-line side operational amplifier.

The effects of the present invention described above are listed as follows. By performing switching control of the analog system, the 2B1Q system, and the ping-pong system by the control unit 20b, the three systems can be realized by one circuit.

The operation of the operational amplifier for signal output can be suppressed to about the signal voltage by separating the operational amplifier of the common circuit of the three systems from the signal output section and the DC component output section by the bias section. Speedup can be realized.

Further, since the high-speed operation is not required for the operational amplifier in the bias section for supplying the bias voltage, an operational amplifier having a high withstand voltage can be realized. Therefore, a high withstand voltage and high speed operational amplifier can be simultaneously realized, and the analog system, the 2B1Q system, and the ping-pong system can be realized by one circuit.

[0097]

As described above in detail, according to the present invention, (1) in a subscriber circuit realizing an analog system, a 2B1Q system, or a ping-pong system, a signal processing unit outputs a transmission signal. The signal output section is divided into a bias section for supplying a bias voltage, and the signal output section is configured with a low-breakdown-voltage, wide-band amplifier section, and the bias section is configured with a high-breakdown-voltage, narrow-band amplifier section. The effect is obtained.

According to the configuration of the present invention, the switching control section for switching the circuit controls the disconnection and connection of the feedback circuit, and switches the phase compensation of the signal output section, thereby achieving the analog system, the 2B1Q system, and the like.
A subscriber circuit that can be commonly used for a ping-pong type circuit can be provided.

Also, the signal output section for signal output and the bias section for supplying a bias voltage are divided into two sections. The operational amplifier constituting the signal output section has a low breakdown voltage and a wide band, and the bias section has a high breakdown voltage and a narrow breakdown voltage. With the use of the band amplifier section, it is possible to provide a subscriber circuit capable of realizing an operational amplifier having a high withstand voltage and a wide band.

(2) In this case, switching or disconnection of the phase compensation circuit of the amplifier section of the signal output section is performed to switch or disconnect the phase compensation circuit of the amplifier section of the signal output section. By
The subscriber circuit can be shared by the analog system, the 2B1Q system, and the ping-pong system.

(3) The feedback circuit from the signal receiving unit to the signal output unit for receiving the received signal is connected in the case of the analog system and disconnected in the case of the 2B1Q system or the ping-pong system. The feedback circuit from the signal receiving unit to the signal output unit is connected in the case of the analog system, and is disconnected in the case of the 2B1Q system or the ping-pong system, and the subscriber circuit is analog system, 2B
1Q system and ping-pong system can be shared.

(4) Further, by switching the external terminating resistor in the analog system, the 2B1Q system, or the ping-pong system, the external terminating resistor is switched in each system, and is most suitable for each system. Termination can be performed.

(5) The external terminating resistor is set to an intermediate value between the ping-pong system and the 2B1Q system, and switching between this resistor and the internal terminating resistor in the analog system is controlled, so that the external terminating resistor can be switched between the 2B1Q system and the ping-pong system. Can be shared.

(6) Further, by inserting a common mode choke coil between the A line and the B line, a common mode choke coil is inserted between the A line and the B line, so that the A line side operational amplifier and the B line side operational amplifier are inserted. , It is possible to suppress distortion from a differential signal due to a difference between positive and negative slew rates caused by speeding up.

As described above, according to the present invention, first, there is provided a subscriber circuit which can be used in common with the above three methods and which can realize an operational amplifier having a high withstand voltage and a wide band. be able to.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between AP1 and AP2 power supplies and an operational amplifier following the power supply;

FIG. 4 is a circuit diagram showing another embodiment of the present invention.

FIG. 5 is a comparative explanatory diagram of each subscriber system.

FIG. 6 is a diagram showing a configuration example of a conventional analog subscriber circuit.

FIG. 7 is a diagram illustrating a configuration example of an operational amplifier.

FIG. 8 is a diagram illustrating an example of a gain-frequency characteristic of an operational amplifier used in a subscriber circuit.

FIG. 9 is a diagram illustrating a configuration example of a conventional 2B1Q subscriber circuit.

FIG. 10 is a diagram showing a configuration example of a conventional ping-pong type subscriber circuit.

[Explanation of symbols]

 2A feedback circuit 3 amplifier 4 amplifier 8 signal receiving unit 20 switching control unit 30 bias unit 40 signal output unit

Claims (6)

[Claims] In a subscriber circuit for realizing an analog system, a 2B1Q system, or a ping-pong system, a signal processing unit is divided into a signal output unit for outputting a transmission signal and a bias unit for supplying a bias voltage. A subscriber circuit comprising a low-voltage, wide-band amplifier section and a bias section with a high-voltage, narrow-band amplifier section. 2. The subscriber circuit according to claim 1, wherein switching or disconnection of a phase compensation circuit of an amplifier section of said signal output section is performed. 3. A feedback circuit for receiving a received signal from a signal receiving section to a signal output section is connected in the case of an analog system and is disconnected in the case of a 2B1Q system or a ping-pong system. Item 3. The subscriber circuit according to Item 1. 4. An external terminating resistor is provided in an analog system
2. The subscriber circuit according to claim 1, wherein the switching is performed in the case of the B1Q system or the ping-pong system. 5. A ping-pong type external termination resistor, 2B1Q
2. The subscriber circuit according to claim 1, wherein a switching value between the resistor and an analog internal termination resistor is controlled by setting an intermediate value between the two values. 6. The subscriber circuit according to claim 1, wherein a common mode choke coil is inserted between the A line and the B line.