JPS60117810A - Equalizer - Google Patents

Abstract

PURPOSE:To secure the optional frequency characteristics and to facilitate easy handling with good reproducibility for an equalizer, by constituting a circuit with capacitors, resistances and an amplifier so that the pole on an S plane can be set on both a real axis and an imaginary axis. CONSTITUTION:For an amplifier A1, the 1st time constant circuit where a resistance R1 and a capacitor C1 are connected in parallel to each other and the 2nd time constant circuit containing a resistance R4 and a capacitor C4 connected in parallel to each other are connected in series between a non-inverse input terminal (+) and a signal input terminal IN. Furthermore a resistance R5 is set at a reference potential from a non-inverse input terminal. While the positive feedback is applied to a serial junctures of both constant circuits from an output terminal OUT of the amplifier A1 through a resistance R2. In addition, a resistance R7 is provided to an inverse input terminal (-) from the output terminal together with a resistance R6 provided between the inverse input terminal and the reference potential. In such a way, the transmission characteristics which could not be attained by a circuit consisting of a CR only can be obtained by applying the positive feedback to the serial junctures of both time constant circuits.

Description

[Detailed description of the invention] The present invention relates to an equalizer in transmission equipment.

In wired communications using transmission lines such as copper cables, equalizers are installed in repeaters to compensate for transmission waveform distortion due to the frequency characteristics of the transmission line. It is considered to be an equalizer with

Conventional equalizers are configured to obtain desired frequency characteristics using a coil and a capacitor when the transmission signal band is a high frequency excluding the audio band.

With this conventional equalizer, it is difficult to obtain frequency characteristics with high Q (selectivity) due to the resistance of the coil, and it is difficult to handle and expensive as it requires obtaining a coil that matches the coil constant and magnetic shielding. Become something.

An object of the present invention is to provide an equalizer that has arbitrary frequency characteristics, has good reproducibility, and is easy to handle.

The present invention is characterized by a circuit configuration that includes a capacitor, a resistor, and a high gain amplifier, and can set the pole in the S plane both on the real axis and on the imaginary axis.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

The amplifier A-1 is a high gain amplifier with a very large input impedance and a very small output impedance, for example, an operational amplifier is used. Amplifier A1 has a resistor R between its non-inverting input terminal (+) and signal input terminal (IN).
A first time constant circuit has a resistor R4 and a capacitor C1 connected in parallel, and a second time constant circuit has a resistor R4 and a capacitor C4 connected in parallel. provided. Also, amplifier A1
Positive feedback is applied from the output terminal (signal output terminal OUT) to the series connection point of both time constant circuits through the resistor R2, and further, a resistor R7 is provided from the output terminal to the inverting input terminal (-), and the inverting input terminal A resistor R6 is provided between the reference potential and the reference potential.

In this way, by applying positive feedback to the series connection point of both time constant circuits, a characteristic of the present invention is that transfer characteristics that cannot be achieved with a circuit consisting only of CRs can be obtained. The transfer function in this embodiment is the output signal Vo for the input signal Vin.
The following equation (1) is obtained as ut.

±5Gs(CI+C4)+5Ca(G1+(1-K)G
2) +S”CsC4・・・・・・・・・・・・(1) Here, K is the set gain of amplifier A1, and −(1+
R7/R6), G1-G5 are respectively 1/R1 to 1/R5,
S=juJ As is clear from equation (1), the pole in the S plane can exist on the real axis or the imaginary axis depending on the value of each constant, and in a normal CR-only circuit, the pole in the S plane By comparing poles and zeros in which can only exist on the real axis, it is possible to obtain arbitrary frequency characteristics by arbitrarily setting the poles that determine the form of change in response over time. And since a coil is not required, a capacitor with high performance can be obtained easily, and unlike a coil, a capacitor is small and does not require a magnetic shield. Furthermore, it is composed of only one amplifier and CR,
This results in a circuit with good reproducibility, low output impedance, easy cascade connections, and the ability to easily realize complex characteristics.

FIG. 2 shows another embodiment of the invention. In the figure, the non-inverting input terminal and signal input terminal (IN
), a first parallel circuit of a capacitor C1 and a resistor R1 is provided between the capacitor C1 and a resistor R1, one end of the parallel circuit of a capacitor C2 and a resistor R2 is connected to the non-inverting input terminal, and the other end is connected to a resistor R.
A is connected to the reference potential via a, and a resistor R4 is further connected between the connection point with the resistor R3 and the output terminal (OUT) of the amplifier A1. Further, a resistor R6 is provided between the inverting input terminal and the output terminal of the amplifier A1, and a resistor R5 is further provided between the inverting input terminal and the reference potential.

Even in this configuration, the pole in the S plane can be made to exist on the real axis or the imaginary axis depending on the value of each constant, and the same effect as in the case of FIG. 1 can be obtained. The transfer function of this example is 0, where ω0IQ01 ω0'
, the QoI is as follows.

10CIRt(RzR4-1-R3R4+2RzRs≠K
R2R3) Figure 3 shows another embodiment of the invention. The inverting input terminal of high gain amplifier A1 has a C between it and the signal input terminal.
A series circuit of two time constant circuits, IRI and CsR5, is provided, a resistor R2 is provided between the series connection point and the reference potential, and a capacitor C4 is provided between the series connection point and the output terminal of the amplifier A1. . A resistor 1ta is provided between the output terminal and the inverting input terminal of the amplifier A1, and the non-inverting input terminal is connected to a reference potential.

Although this embodiment uses negative feedback, the poles of the 5sfL plane can be placed on the real axis and on the imaginary axis as in the previous embodiments. Also, the input and output phases are reversed. The transfer function of this embodiment is expressed by the following equation.

As described above, since the equalizer according to the present invention obtains arbitrary frequency characteristics using an amplifier, a capacitor, and a resistor, it has various effects such as easy handling and good reproducibility. This has the effect of allowing recognition anywhere on the imaginary axis.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are circuit diagrams showing each embodiment of the present invention.

Claims (3)

[Claims] (1) A high gain amplifier with high input impedance and low output impedance; a resistor provided between the non-inverting input terminal and the signal input terminal of this amplifier; a first time constant circuit and a second time constant circuit in parallel with the capacitor; a series connection circuit, a first resistor provided between the non-inverting input terminal of the amplifier and a reference potential, and a connection point between the output terminal of the amplifier and the first and second time constant circuits. a #g3 resistor provided between the output terminal of the amplifier and the inverting input terminal of the amplifier, and a fourth resistor provided between the inverting input terminal of the amplifier and the reference potential. An equalizer. (2) A high-gain amplifier with high input impedance and low output impedance, a first time constant circuit in which a resistor and a capacitor are connected in parallel, and which are installed between the non-inverting input terminal and the signal input terminal of this amplifier, and the non-inverting circuit of the above-mentioned amplifier. a second time constant circuit of a resistor and a capacitor string, one end of which is connected to the input terminal and the other end of which is connected to a reference potential via a first resistor; and an output terminal of the amplifier and the second time constant circuit. and a connection point of the resistor of rattan 1; a third resistor provided between the output terminal of the amplifier and the inverting input terminal of the amplifier; and a third resistor provided between the output terminal of the amplifier and the inverting input terminal of the amplifier. and a fourth resistor provided between the reference potential and the reference potential. (3) A first case in which a high gain amplifier with a non-inverting input terminal set to a reference potential, high input impedance and low output impedance, and a parallel resistor and capacitor provided between the inverting input terminal and the signal input terminal of this amplifier. a series connection circuit of a constant circuit and a second time constant circuit; a first resistor provided between a connection point of the first and second time constant circuits and a reference potential;
An equalizer comprising a capacitor provided between the connection point of the first and second time constant circuits and the output terminal of the amplifier, and a second resistor provided between the output terminal of the amplifier and the non-inverting input terminal. .