JPS6310615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic hybrid circuit suitable for changing the impedance of a two-wire balanced signal line (hereinafter abbreviated as two-wire) to a complex impedance.

Conventionally, electronic hybrid circuits have used a configuration as shown in FIG. 1 in terms of an AC equivalent circuit, in which an amplifier 1 outputs a complementary voltage, an output resistor 2 each having an equal resistance value R ₁ /2, differential amplifier 3,
4, passive circuits 5 and 6, and a voltage amplifier 7. To explain the circuit operation, a 4-wire unbalanced (hereinafter abbreviated as 4-wire) input signal applied to terminal 8.
V _R is input to an amplifier 1, and its complementary output is output to two-wire terminals 9 and 10 via an output resistor 2.

On the other hand, the two-wire signal input to the terminals 9 and 10 is outputted to the terminal 11 as a four-wire output signal V _S via the differential amplifiers 3 and 4. At this time, the 4-wire input signal
In order to suppress V _R from entering the 4-wire output signal V _S , the 4-wire input signal V _R passes through passive circuits 5 and 6 with impedances Z ₂ and Z ₃ , and an amplifier 7, and is subtracted by a differential amplifier 4. is being carried out. Because of this configuration, the two-wire termination impedance V _2W is given by twice the resistance 2, and the termination impedance V 2W is given by twice the resistance 2.
There is no problem if V _2W is a pure resistance, but for example, if you try to design the terminal impedance V _2W to be equivalent to a series impedance of a capacitance of 1 μF and a resistor of 600 Ω, the resistor 2 part will be replaced with a series circuit of a capacitance of 2 μF and a resistor of 300 Ω. The need arose, and at that time the 2 μF capacitor had the drawback of requiring a fairly large volume element due to its large capacitance value and withstand voltage, resulting in a decrease in packaging density and an increase in price.

In order to eliminate these drawbacks, the present invention provides two
A passive circuit that provides line termination impedance is used in the feedback loop, and if the passive circuit includes capacitance or inductance, the required capacitance or inductance value and withstand voltage are kept low, and the size of the capacitance or inductance is reduced. The purpose is to lower prices. The drawings will be explained in detail below.

FIG. 2 shows a first embodiment of the present invention and only shows an AC equivalent circuit. The circuit is a differential amplifier 1
The current amplifier 16 is an amplifier that outputs an input current as a complementary current. Here differential amplifiers 12 and 13,
Transistor 15, passive circuit 17, current amplifier 1
6 constitutes a circuit that provides two-wire termination impedance, and passive circuits 18 and 19 constitute a circuit for suppressing the signal applied to the four-wire input terminal 24 from flowing into the four-wire output terminal 23. Note that the differential amplifier 13 may be incorporated into the differential amplifier 12. To explain the operation of this circuit, the signals input to the two-wire input terminals 20 and 21 are sent to the differential amplifier 1.
2, the differential signal is output to the terminal 22, and the output is output to the 4-wire output terminal 23 via the differential amplifier 14. On the other hand, the signal applied to the 4-wire input terminal 24 is input to the differential amplifier 13, and its output is input to the base 32 of the transistor 15 and is converted into voltage/current by the impedance Z ₁ of the passive circuit 17 connected to the emitter 26. The converted current is output to the collector 27. The output passes through a current amplifier 16, and complementary output currents are output to two-wire input terminals 20 and 21. That is, differential amplifier 1
3. The current converted by the conversion circuit including the transistor 15 and the passive circuit 17 is outputted to the two-wire input terminals 20 and 21 as complementary output currents via the current amplifier 16. Further, the signal applied to the 4-wire input terminal 24 is voltage-divided by the passive circuits 18 and 19 and input to the differential amplifier 14, thereby suppressing the signal from going around from the 4-wire input to the 4-wire output.

At this time, the characteristics of the circuit are Z _IN =Z ₁ /g ₁ g ₂ g ₃ (1) G _2W → _4W =g ₂・g ₄ (2) G _4W → _2W = 1/g ₂・Z _L /Z _L +Z _IN (3), and the balance condition is Z _L /Z _IN =Z ₃ /Z ₂ (4). However, Z _IN is the impedance seen from the 2-wire input terminals 20 and 21 into the hybrid circuit, g ₁ ,
g ₂ , g ₃ , and g ₄ are the amplification factors of the current amplifier 16 and differential amplifiers 12, 13, and 14, respectively; Z _L is the impedance seen from the two-wire input terminals 20 and 21 toward the telephone side;
G _2W → _4W means that the voltage between 2-wire input terminals 20 and 21 is 4
Voltage gain output to line output terminal 23, G _4W → _2W
is the voltage at the 4-wire input terminal 24 is the 2-wire input terminal 20,
This is the voltage gain output between 21 and 21.

As can be seen from equation (1), the two-wire impedance
Z _IN is proportional to the impedance Z ₁ of the passive circuit 17,
Its proportionality constant is 1/g ₁ g ₂ g ₃ . For example, if you want to realize a series impedance of 1 μF capacitance and 600 Ω resistor as Z _IN , the configuration of Z ₁ is 1/g ₁ g ₂ g ₃ μF capacitance and 600 × (g ₁ g ₂ g ₃ ) Ω resistor in series. It becomes a circuit,
If the product of g ₁ g ₂ g ₃ is chosen to be larger than 1, a small capacity will be required and the initial objective will be achieved.

FIG. 3 shows a second embodiment of the present invention.
In the figure, Z ₁ is designed so that Z _IN is equal to Z _L , and the passive circuits 18 and 19 are replaced with an amplifier 28 with an amplification factor of g _5. The amplifier 28 can be realized by simply resistive voltage division.

At this time, the characteristics of the circuit are expressed by equations (1), (2), (3), and (4), where Z _L =
By setting Z _IN , Z _IN = Z ₁ /g ₁ g ₂ g ₃ (5) G _2W → _4W = g ₂・g ₄ (6) G _4W → _2W = 1/2g ₂ (7), and the balance The condition is g ₅ = 1/2 (8). Generally Z _L is a complex impedance,
Since it is approximated by about 2 to 6 elements, Z ₁ must also be a complex impedance in order to set Z _IN = Z _L , but Z ₂ and Z ₃ in Fig. 2 are simply amplifiers 28
Therefore, in the circuit of FIG. 3, only one complex impedance _Z1 is required. Furthermore, as can be seen from equations (6) and (7), since the transfer function between two and four wires is a real number, the frequency characteristics are flat and the transmission characteristics are also excellent.

FIG. 4 shows still another circuit configuration example of the partial circuit consisting of the transistor 15 and the passive circuit 17 in FIGS. 2 and 3.
0 and a passive circuit 31. In this example circuit
Z _IN = 1/g ₁ g ₂ g ₃ g ₆ g ₇・₁ /Z ₄ .

However, g ₆ and g ₇ are voltage-current conversion circuit 2, respectively.
With a conversion factor of 9.30, Z ₄ is given by the impedance of the passive circuit 31. That is, by using the partial circuit shown in FIG. 4, an impedance Z _IN proportional to the reciprocal of the passive circuit 31 can be realized. This means that Z ₄
Using capacitance, Z _IN becomes inductance,
Conversely, it is shown that Z _IN can be designed as a capacitance if an inductance is used for Z ₄ .

In the above embodiments, the voltage signal is converted into a current signal,
It is clear that by substituting voltage signals for current signals, the amplifier also operates by substituting current and voltage types. Further, the transistor 15 is
It is also clear that PNP types or FETs can be used.

FIG. 5 shows a more specific circuit configuration of this embodiment. The circuit components in FIGS. 2 and 3 respectively correspond to the circuit components in FIG. 5 as follows. That is, the two-wire input terminals 20, 2
1 is 2W, differential amplifier 12, g ₂ is current amplifier
A conversion circuit comprising A ₁ , A ₂ , B ₂ , output terminal 22 at point Q, differential amplifier 13 , g ₃ for current addition at point Q, transistor 15 and passive circuit 17 , Z ₁ is a circuit. B ₁ is the passive circuit 17, Z ₁ is the circuit
B ₁ impedance Z _X , current amplifier 16, g ₁
corresponds to circuit B ₃ and current amplifiers C ₁ and C ₂ , voltage amplifier 28 and g ₅ correspond to the 1:1/2 output of current amplifier E ₂ , and differential amplifier 14 and g ₄ correspond to circuit E ₁ . Furthermore, the fifth
In the figure, I _L is the communication current, V _L is the voltage between the two-wire input terminals 2W, V _BB is the power supply voltage, and Vref is given within the range that does not saturate each transistor Q ₁ , Q ₂ , Q ₄ in circuit B ₃ . A suitable voltage, e.g. -5V, C _DC is the capacity for current supply to the telephone. In addition, current amplifiers A ₁ , A ₂ ,
B ₂ , C ₁ , C ₂ , and E ₂ are equipped with current mirror circuits (for example, “Analysis and Design of Analog
Integrated Circuit”Paul R, Gray, Robert
G. Meyer: John Wiley & Sons, 1977 p.197~
261 In particular, Fig. on p.233 and 236) can be used.

Next, the operation of this circuit will be explained. First, we will discuss the operation of DC characteristics.

The voltage drop between the base and emitter of the transistors in current amplifiers A ₁ and A ₂ is small compared to the current voltage V _BB , so if ignored,
A ₁ , resistor R ₂ , 2W, resistor R ₁ , current amplifier A ₂ ,
The current flowing through the resistor R ₁ on the path to the V _BB power supply is |V _BB |−V _L /2R ₁ , which becomes the input current of the current amplifiers A ₁ and A ₂ , and the output of the current amplifier A ₁ is the current amplifier. B ₂ and its output is the output of current amplifier A ₂ and point P,
are added at Q. Also, n of current amplifier _C1 :
n/2 of the line current I _L is added to the 2 output of 1:2 at the flow point P, and their sum (|V _BB | −V _L /2R ₁・2−I _L /n/2) is input to the bases of transistors Q ₁ and Q ₂ in circuit B ₃ . The current amplified by the transistors Q ₁ and Q ₂ and the current flowing from the circuit B ₁ to the circuit B ₃ are added and input to the current amplifier _{C 2 .}
The n output of 1 is connected to the 2WA terminal, the output of 1 is input to the current amplifier _C1 , and the n output of n:1:2 is connected to the 2WB terminal.

This DC circuit only works for DC and not for AC signals due to the capacitance C _DC in circuit _B3 . Next, the operation of AC characteristics related to the present invention will be described.

The voltage at the 2W end is determined by current amplifiers A ₁ , A ₂ and resistors.
Voltage/current conversion is performed at _R1 , and the output of current amplifier _A1 is input to current amplifier _B2 , and its output is added to the output of current amplifier _A2 at point Q, thereby detecting the differential signal at the 2W end. be done. This current is input to circuit B ₁ , and the operational amplifier operates in such a way that a potential drop equal to the potential drop generated across resistor R ₂ occurs at impedance Z _X , and the collector current of transistor Q ₃ is input to circuit B ₁ . The resulting current is multiplied by R ₂ /Z _X. This current is input into the current amplifier C ₂ through the common base transistor Q ₄ in the circuit B ₃ , and the n output of n:1:1 is the 2-wire input.
The output of 1 is outputted to 2WA, and the output of ₁ is n
It is multiplied and output to 2WB of 2-wire input.

Also, the signal from the 4-wire input 4WR is capacitance and resistance.
Voltage-to-current conversion is performed by R ₄ and current amplifier E ₂ , and the output is added to point Q. (Differential amplifier 13,
Corresponds to the function of g ₃ . ) Also, for signal transmission from 2 wires to 4 wires, the 2 wire signal is converted into voltage and current by current amplifiers A ₁ and A ₂ and resistor R ₁ , and the output of current amplifier A ₁ is input to current amplifier B ₂ , and its The output is added to the output of the current amplifier _A2 at point S, and is outputted to the four-wire output _4WS via the left-handed amplifier E1. For echo suppression, the 4-wire input 4WR signal is converted into a current and output to the 1:1/2:1 1/2 output of current amplifier _E2 , which is input to differential amplifier _E1 to suppress the echo. .

_{Expressing the above circuit} characteristics using formulas _{, Zin = R 1 ・ Z} ), and the cancellation condition is Zin=Z _L Output from E ₂ to E ₄ : 1/2 (12).

As explained above, by inserting a passive circuit with impedance Z ₁ or Z ₄ into the feedback loop to provide the 2-wire side impedance Z _IN of the electronic hybrid circuit, the 2-wire side impedance Z _IN is proportional or inversely proportional to the impedance Z ₁ or Z ₄ , and by appropriately selecting the proportionality constant or inverse proportionality constant, the element value of the capacitance or inductance used for the impedance Z ₁ and Z ₄ can be selected to be small, and the element size Since the circuit can be designed so that the voltage applied to the impedance Z ₁ or Z ₄ is smaller than the DC voltage applied to the two-wire input terminal, a low withstand voltage element can be used. It is effective for downsizing and economical elements of passive circuits with impedance Z ₁ or Z ₄ .

[Brief explanation of the drawing]

Figure 1 shows a conventional electronic hybrid circuit; Figure 2 shows a conventional electronic hybrid circuit;
The figure shows the first embodiment of the present invention, FIG. 3 shows the second embodiment of the present invention, FIG. 4 shows another circuit configuration example of the partial circuit in the first and second embodiments, and FIG. It is a specific circuit configuration of an example. 1...Amplifier, 2...Output resistance, 3, 4, 1
2, 13, 14...Differential amplifier, 5, 6, 17,
18, 19... Passive circuit, 7, 28... Voltage amplifier, 8, 24... 4-wire input terminal, 9, 10, 2
0, 21... 2-wire input terminal, 11, 23... 4-wire output terminal, 15... transistor, 16... current amplifier, 22, 25... output terminal, 26... emitter, 27... collector, 32 ...Base, 2
9, 30...Voltage-current converter, 31...Passive circuit, _A1 , _A2 , _B2 , _C1 , _C2 , _E2 ...Current amplifier.

Claims (1)

[Claims] 1. A circuit whose input impedance is a complex impedance and which provides a 2-wire terminal impedance, a 4-wire line-2-wire line signal transmission section, and a 2-wire line-4 In an electronic hybrid circuit comprising a wire line signal transmission section, the circuit providing the two-wire termination impedance includes a detection circuit _g2 that detects a two-wire input signal, converts it into an unbalanced signal, and outputs it; The output of the detection circuit and 4
a circuit g 3 that inputs a line unbalanced input signal and outputs the difference between the two inputs; and a passive circuit that inputs the output of _{the circuit g 3 that} outputs the difference between the two inputs, and has an impedance Z ₁ ; The impedance Z ₁
Active circuit 1 that converts and outputs a signal determined by
5, and a feedback circuit including a current amplifier _g1 which receives the output from the conversion circuit and outputs a complementary current to the two-wire balanced signal line, The 2-wire line-to-4-wire line signal transmission unit includes a circuit _g3 that outputs the difference between the two inputs, the conversion circuit, and the current amplifier _g1 ; Output signal 22 of the detection circuit g2 of the feedback circuit configuring the circuit providing the _two -wire termination impedance
and an output signal obtained by applying the 4-wire unbalanced input signal to the balanced network Z ₂ , Z ₃ , g ₅ or E ₂ and outputs _a difference. Electronic hybrid circuit. 2 The balance network has resistive partial voltages Z ₂ ,
2. The electronic hybrid circuit according to claim 1, characterized in that it is constituted by _Z3 , voltage amplifier _G5 , or current amplifier _E2 . 3 The signal determined by the impedance Z ₁ is:
2. The electronic hybrid circuit according to claim 1, wherein the electronic hybrid circuit comprises a signal proportional to the impedance _Z1 . 4 The signal determined by the impedance Z ₁ is
2. The electronic hybrid circuit according to claim 1, wherein the electronic hybrid circuit comprises a signal that is inversely proportional to the impedance _Z1 .