JPS6053482B2 - variable equalizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1) Field of Application of the Invention The present invention relates to a variable equalizer that is inserted into a transmission path and whose frequency characteristics can be varied to compensate for changes in the frequency characteristics of the transmission path. It is.

(2) Prior Art Conventionally, a Bode type variable equalizer is commonly used, and the frequency characteristics are made variable by changing one resistor.

However, since this equalizer requires an inverse circuit, if a capacitor is used in one circuit, an inductance is necessarily required in the other circuit, making it unsuitable for IC and miniaturization of the circuit. (3) Object of the Invention The present invention eliminates the above-mentioned drawbacks and provides a variable equalizer that does not include inductance.

(4) General description of the invention FIG. 1 is a circuit diagram of a variable equalizer according to the invention.

In FIG. 1, a signal of voltage V1 is applied to the input signal terminal 2, and a connection point 8 between the resistor 5 and the impedance circuit 7 is applied.
The subtraction circuit 9 extracts the difference between the voltage V' generated in
If the gain of amplifier 1 is ・G, then the voltage generated at output signal terminal 3 of amplifier 1 is: Hato becomes.

On the other hand, a resistor 5 (its value Rx) is connected in series with a voltage source 4 that generates a voltage h1 times the output signal voltage VO, and an output signal voltage VO? An impedance circuit (its value Z) is connected in series with the voltage source 6 that generates twice the voltage.
When these are connected in parallel, the voltage v'' generated at the connection point 8 is expressed as follows.

however It is.

Here ■ is a constant. From equations (1) and (2), V
If we eliminate ``, then when the gain G of the amplifier 1 is large, we get the following equation.If we give z of the impedance circuit 7 a frequency characteristic, then by varying the resistance value Rx of the resistor 5, equation (4) becomes It shows a symmetrical variable HlZ characteristic and satisfies the conditions for a variable equalizer.

FIG. 2 shows the frequency characteristics of the circuit configuration shown in FIG. When the resistance value RX of resistor 5 is 0, the characteristic is shown in blue,
When RX is infinite, the characteristic is 1
．． R0, Ru.

Moreover, when RX=circle, it shows the standard characteristic of H7-2-.
It goes without saying that the subtraction circuit 9 described here may be replaced by an addition circuit depending on the polarity of the voltage sources 4 and 6 or the polarity of the output of the amplifier 1.

Furthermore, as is clear from equation (2), the circuit constituted by the voltage sources 4, 6, the resistor 5, and the impedance circuit 7 alone has characteristics as a variable equalizer. Furthermore, according to the circuit configuration of the present invention, it is possible to obtain an output signal directly from the amplifier without going through a resistor circuit, so by making the output impedance of the amplifier sufficiently small, it is possible to It has the advantage of reducing restrictions. (5) Examples Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 3 is an example of the embodiment shown in FIG.

The parts corresponding to the subtraction θ subtraction circuit 9 and amplifier 1 in FIG.
In the figure, this is realized using a differential amplifier 10. Also the first
In Figure 3, the output of the differential amplifier 10 is h1.
5 is formed through a circuit network 11 with a transfer function of , and a voltage follower 13 with a gain of 1; The voltage source 6 shown in FIG. 1 is formed.
The circuit networks 11 and 12 can be realized by resistors and capacitors as shown in FIG. 4, and the impedance circuit 7 can be realized by a circuit as shown in FIG.

These circuit formats are determined by the required variable characteristics, and FIGS. 4 and 5 are examples thereof. Transfer function h1 of network 11, transfer function of network 12 and impedance 17 of impedance circuit 7. If Z satisfies the condition of equation (3), the circuit of FIG. 3 operates as a variable equalizer by varying the resistance x of the resistor 5.

FIG. 6 shows an example when h1=1.

In this case, the network 11 and voltage follower 1 of FIG.
3 can be omitted. Also, as is clear from equation (3), the sixth
The transfer function of network 12 in the figure requires that .

The circuit network 12 and impedance circuit 7 in FIG. 6 can be realized by circuits as shown in FIGS. 4 and 5, respectively.
FIG. 1 is an equivalent transformation of FIG. 6.

In FIG. 7, if the resistance value of resistor 15 is Ra, and the impedances of impedance circuits 16 and 17 are respectively H, then the following conditions need to be satisfied for this to be equivalent to that in FIG.

FIG. 8 is an example that embodies FIG. 7.

The circuit type of the impedance circuits 16 and 17 is determined by the required variable characteristics as described above. (6)
Summary As explained above, according to the present invention, a variable equalizer can be constructed without using an inductance, and the problems of miniaturization and integration of conventional variable equalizers into ICs can be solved, and the effects are extremely high. big.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of the present invention, FIG. 2 is a frequency characteristic diagram of a variable equalizer according to the present invention, and FIGS. 3, 6, 7, and 8 are diagrams showing an embodiment of the present invention. FIG. 4 is a diagram showing a concrete example of the transfer functions 11 and 12, and FIG. 5 is a diagram showing a concrete example of the impedance circuit 7.

Claims (1)

[Claims] 1. A differential amplifier that amplifies the difference between a transmission signal input to a first input terminal and a feedback signal input to a second input terminal and outputs the amplified signal from an output terminal, and a variable resistor. a circuit in which a first transmission means is connected in series, and a circuit in which an impedance circuit and a second transmission means are connected in series, the variable resistance side and the impedance circuit side are connected to the second input end side, and the The first transmission means side and the second transmission means side are respectively connected to the output end side, and the transfer function h_1 of the first transmission means, the transfer function h_2 of the second transmission means, and the value Z of the impedance circuit are R
A variable equalizer characterized by having a relationship h_1/h_2=(R_0/Z)^2 where _0 is a constant. 2. The variable equalizer according to claim 1, wherein the transfer function h_1 of the first transfer means is set to h_1=1.