JPS6130776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic hybrid circuit that connects a two-wire line and a four-wire line.

A hybrid circuit that connects a two-wire line and a four-wire line has generally been constructed using a hybrid coil. Since this hybrid coil is made by winding a coil around a magnetic core, it is difficult to miniaturize it, and since it includes a winding process, it is difficult to reduce manufacturing costs. Therefore, electronic hybrid circuits have been proposed, but because they require a large number of high-performance differential amplifiers, they are expensive and have relatively high power consumption.

The present invention improves the above-mentioned drawbacks, and aims to provide an economical configuration by reducing the number of differential amplifiers. Examples will be described in detail below.

Figure 1 is a block diagram of the conventional example, where 1 is 4.
Input terminal of wire line, 2 is output terminal of 4-wire line, 3 is input/output terminal of 2-wire line, 4 is balanced output amplifier, 5 is balanced network, 6 to 8 are differential amplifiers, R ₁ to _R5 are resistances, and Z is the impedance of the two-wire line. balance network 5
has the circuit configuration shown in FIG. 2, for example, in which a resistor R ₆ is connected between terminals a and c, a resistor R ₇ is connected between terminals b and d, and a pseudo load Zp is connected between terminals a and b. The pseudo load Zp simulates a two-wire line, and has a circuit configuration including a capacitor and the like so that the same time constant as that of the two-wire line can be obtained. The impedance of this pseudo load Zp is 2
The impedance Z of the wire line is multiplied by α, and the time constant is the same. In this way, in response to increasing the impedance of the pseudo load Zp, the resistors R ₆ and R ₇ are also increased. If the nominal impedance is R ₀ , the resistors R ₆ and R ₇ are α・R ₀ /2. selected. If the time constant of the pseudo load Zp is kept constant and its impedance is increased, in the case of a circuit configuration consisting of a resistor and a capacitor, the resistance value will be increased and the capacitance of the capacitor will be reduced.
It is possible to downsize the capacitor that forms part of Zp.

When looking from the input/output terminal 3 of the 2-wire line to the input terminal 1 side of the 4-wire line, the output impedance of the amplifier 4 is small, so it is terminated with a nominal impedance R ₀ , and the input terminal 1 is applied to the input terminal 1. The signal is converted into a balanced output by the amplifier 4 and output to the input/output terminal 3 via matching resistors R ₄ and R ₅ .
Further, the signal applied to the input/output terminal 3 is outputted to the output terminal 2 via differential amplifiers 8 and 6. Further, the output of the amplifier 4 is connected to the terminal c of the balance network 5,
d, and is also applied to the differential amplifier 8 via matching resistors R ₄ and R ₅ , but the signals appearing at terminals a and b of the balance network 5 are the same as the signals appearing at the input/output terminal 3. is similar to, but in reverse phase, so when the output of differential amplifier 7 and the output of differential amplifier 8 are combined via resistors R ₂ and R ₃ ,
They cancel each other out. Therefore, the suppression of the signal from the input terminal 1 to the output terminal 2, that is, the amount of sound attenuation can be increased.

The present invention further reduces the number of differential amplifiers by using a switched capacitor circuit. FIG. 3 shows a block diagram of an embodiment of the present invention, and the same symbols as in FIG. 1 are the same. _C1 to _C4 are capacitors, _S1 to _S5 are switches composed of transistors, etc., and 9 is a differential amplifier. The switches S ₁ to S ₅ switch in synchronization and are controlled at a frequency higher than the signal frequency.

In a switched capacitor circuit, a signal is applied to both ends of a capacitor via a switch, a charge corresponding to the level difference between the signals at both ends is stored in the capacitor, and the charged charge is output by switching the switch. Yes, therefore switches S ₂ and S ₃
The switched capacitor circuit consisting of the switches S ₄ and S ₅ and the capacitor C ₃ performs the function equivalent to the differential amplifier ₇ in FIG. It performs an action corresponding to the differential amplifier 8 of FIG. 1. Furthermore, the switched capacitor circuit consisting of the switch _S1 and the capacitor _C1 , the capacitor _C2 , and the differential amplifier 9 performs the same function as the differential amplifier 6 in FIG.

When switches S ₂ to _{S 5} are in the state shown, the capacitor
_C3 is charged by the signals appearing at terminals a and b of the balance network 5. Also capacitor C ₄
is charged by the signal appearing at the input/output terminal 3. At this time, if the switch S ₂ side is set to +, the switch S ₅ side becomes + because it is connected via the resistor R ₅ and the balance network 5, and the switch S 5 side becomes +.
The S ₃ and S ₄ sides become -. Therefore, when switches S ₂ to _{S 5} are switched from the illustrated state in the direction of the arrow, the switches S ₂ and S ₄ are connected, and the switches S ₃ and S ₅ are connected, so that the + side of capacitor C ₃ and The negative side of capacitor C ₄ is connected, and the negative side of capacitor C ₃ and the positive side of capacitor C ₄ are connected.

Therefore, among the output signals of the amplifier 4, a signal is charged to the capacitor _C3 via the balance network 5, and a signal is charged to the capacitor C4 via _the resistors _R4 and _R5 .
However, as mentioned above, when switches S ₂ to S ₅ are switched,
Since it will be added with opposite polarity, input terminal 1
It is possible to prevent the leakage from reaching the output terminal 2.

Regarding the input signal from the input/output terminal 3, the signal charged to the capacitor C ₄ and the signal charged to the capacitor C 3 via the resistors R ₄ , R ₅ and the balance network ₅
Since the magnitude of the signal charged in the capacitors C 3 and C is different, when the switches S ₂ to _{S 5} are switched from the state shown in the figure in the direction of the arrow, the voltage is applied with the opposite polarity as described above, but the capacitors C ₃ and C ₄ is input to the differential amplifier 9 as an input signal component, and is output to the output terminal 2 of the 4-wire line.

Furthermore, when the switch _S1 is in the state shown in the figure, the output signal of the differential amplifier 9 is output to the output terminal 2, and
Capacitors C ₁ and C ₂ are charged. Then, when switch S ₁ is switched in the direction of the arrow, the capacitor
_C1 will be connected between the - terminal and + terminal of the differential amplifier 9, and the output signal will be connected to the capacitor.
It is fed back to the - terminal via _C1 . Thereby, the signal from the two-wire line can be output to the output terminal 2 of the four-wire line, similar to the differential amplifier 6 in FIG.

By using the switched capacitor circuit in this way, the amplifiers 4 and 9 as active circuits are
Since the drive power of the switches S ₁ to _{S 5} is extremely small, the power consumption is reduced, and similar to the configuration shown in Fig. 1, the amount of sound attenuation is large, and the two-wire line Since the balance network 5 is well-balanced when viewed from the front, the amount of longitudinal balance attenuation is also large.

As explained above, in the present invention, the first transmission section that sends the input signal of the 4-wire line to the 2-wire line is configured by the balanced output amplifier 4 and the matching resistors R ₄ and R ₅ . The second transmission section that sends the input signal of the two-wire line to the four-wire line is a differential amplifier 9.
, a first switched capacitor circuit forming a feedback circuit consisting of a switch S ₁ and a capacitor C ₁ , and a second switched capacitor circuit consisting of switches S ₄ and S ₅ and a capacitor C ₄ . , the signal suppression circuit is balanced network 5
and a third switched capacitor circuit consisting of switches S ₂ and S ₃ and capacitor C _3. By using the switched capacitor circuit, the number of expensive differential amplifiers can be reduced. Since the switches S ₁ to _{S 5} can be constructed using transistors, the configuration can be small and consume low power.

Furthermore, by using the second switched capacitor circuit and the third switched capacitor circuit via the balance network 5, the amount of sound attenuation can be increased.

Therefore, there is an advantage that a small electronic hybrid circuit can be constructed economically.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional example, FIG. 2 is a circuit diagram of an example of a balance network, and FIG. 3 is a block diagram of an embodiment of the present invention. 1 is an input terminal, 2 is an output terminal, 3 is an input/output terminal, 4 is a balanced output amplifier, 5 is a balanced network, 6 to 9 are differential amplifiers, R ₁ to R ₇ are resistors,
_C1 to _C4 are capacitors, and _S1 to _S5 are switches.

Claims (1)

[Claims] 1. A first transmission section for sending an input signal of the 4-wire line to the 2-wire line, and a second transmission section for sending the input signal of the 2-wire circuit line to the 4-wire line. and a circuit for suppressing a signal from the input side to the output side of the four-wire line, wherein the first transmission section amplifies the input signal of the four-wire line. a balanced output amplifier;
The second transmission section includes a differential amplifier configured to include a matching resistor connected between the output terminal of the amplifier and the two-wire line, and the second transmission section sends a signal to the output side of the four-wire line. , a first switched capacitor circuit forming a feedback circuit of the differential amplifier, and a second switched capacitor circuit for applying the input signal of the two-wire line to the differential amplifier. and the signal suppression circuit includes a balance network connected between the output terminal of the balanced output amplifier and the input terminal of the differential amplifier, and a third switched capacitor circuit. An electronic hybrid circuit characterized by: