JPS6295013A - Variable equalizer - Google Patents

Abstract

PURPOSE:To constitute a variable equalizer by using only one piece of impedance element, by using the first variable resistor and the second variable resistor. CONSTITUTION:One signal input terminal 6 is connected to a base of a transistor 7, and the other signal input terminal 6' is grounded. An emitter of the transistor 7 is connected to a base of a transistor 13 through a variable resistor 10, and the base of the transistor 13 is grounded through an impedance element 9. An emitter of the transistor 13 is grounded through a fixed resistor 14, and a collector of the transistor 13 is grounded through a variable resistor 16 having a value which is equal to that of the variable resistor 10 and also connected to a base of a transistor 11. A collector of the transistor 11 is grounded, and an emitter of the transistor 11 is connected to a collector of the transistor 7 through a fixed resistor having a value which is equal to that of the fixed resistor 14. An output terminal 15 is connected to the collector of the transistor 7, and an output terminal 15' is grounded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a wideband variable equalizer with a simple circuit configuration.

[Conventional technology]

The variable equalizer was invented by H.W. First, to explain the Bode type variable equalizer, Fig. 2 shows its basic configuration. In Fig. 2, 1 and 1' are signal input terminals, 2 and 2' are signal output terminals, and 3 is a signal output terminal. A three-terminal circuit network, 4 is a variable resistor, and 5 and 5' are variable resistor connection terminals.

By the way, according to H, W, and Bode, the transfer admittance Y from the signal input terminal 1.1' to the signal output terminal 2, 2' is. However, R is the variable resistance value, YS is Y when R=O, Yo is Y when R-■ is closed, and Z is the impedance when looking at the 3-terminal network 3 from the connection terminals 5 and 5'.

Here, with Ro as the reference resistance value, Z = J Yo /
If the three-terminal network 3 satisfies Ys-&, e
-Y + e-00=n, z=R/Ro
+ e−ψ”)=z/Ro and perform variable conversion to obtain Equation (1).

When θ in equation (2) is expressed as a Taylor expansion around ψ(ω)−〇 with respect to ψ(ω), the following terms can be ignored and approximated as follows.

Equation (3) is the transmission of the Naper representation as a variable equalizer'!
! f'j cow F(ω) = F, (ω) + F2(R)・F3(ω)
...Add (4).

Here, Fl (ω) represents a fixed equalization characteristic, F2 (R) is a function of only variable resistance value independent of frequency, and F, (ω) represents a variable equalization characteristic.

The same principle applies to Q, Li type, cylindrical/enclosed type, etc.

Based on the theory of variable equalizer shown by Bode, (
2) The circuit configuration that realizes the formula is disclosed in Patent Application No. 56-12226.
It is disclosed in the specification of No. 6. FIG. 3 is a diagram of an embodiment disclosed in this publication. In FIG. 3, 6°6' is a signal input terminal, and 15 and 1.5' are signal output terminals. 7, 11, and 13 are transistors; 8. t
4q+ is a control resistor, 10 is a variable resistor, and 9
, 12 are impedance elements. The impedance elements 9 and 12 are set to have the same phase with each other, and the equalization characteristic of the transfer function from the signal input terminals 6, 6' to the signal output terminals 15, 15' is made variable by the variable resistor 1o. be.

The above variable equalizer j has the excellent feature that it has a simple circuit configuration, does not include a feedback circuit, and can be realized by a single variable resistor with one side grounded. [Problems to be solved by the invention] ] However, the variable equalizer described above is necessarily equipped with two sets of impedance elements. In general, impedance elements have a large number of components and a large circuit scale in order to have desired frequency characteristics, so using two sets of such impedance elements poses a problem in terms of manufacturability.

Furthermore, setting the two impedance elements with high precision requires a lot of adjustment work, which is a similar problem when implementing an integrated circuit.

The present invention provides a variable equalizer that eliminates the above problems.

[Means for resolving issues]

In the present invention, the base of the first transistor and the ground are used as signal input terminals, the emitter of the first transistor and the base of the second transistor are connected via a first variable resistor, and the emitter of the first transistor is connected to the base of the second transistor through a first variable resistor. The base of the second transistor is grounded via an impedance element, and the collector of the second transistor is grounded via a second variable resistor having a value equal to that of the first variable resistor, and is connected to the base of the third transistor. Further, the collector of the third transistor is grounded, the collector of the first transistor and the emitter of the third transistor are connected via the first fixed resistor, and the emitter of the second transistor is connected to the first fixed resistor. This variable equalizer is characterized in that it is grounded via a second fixed resistor having the same value as the resistor, and the collector of the first transistor and the ground are used as signal output terminals.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

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

One signal input terminal 6 is connected to the base of the transistor 70, and the other signal input terminal 11'' is grounded. 1, and the base of the transistor 130 is grounded via an impedance element 9. The emitter of the transistor 13 is grounded via a fixed resistor 14, and the collector of the transistor 13 is connected to a variable resistor having a value equal to that of the variable resistor 10. 16 and is connected to the base of the transistor 11. The collector of the transistor 11 is grounded and connected to the base of the transistor 11.
The emitter of transistor 11 is connected to the collector of transistor 7 via a fixed resistor 8 having the same value as fixed resistor 14 . Output terminal] 5 is transistor 7
The output terminal 15' is grounded.

In Figure 41, the resistance value of fixed resistors 8 and 14 is R.
8. If the resistance value of the variable resistors 10 and 16 is R and the impedance of the impedance element 9 is Z(ω), then the transfer function T(ω) from the signal input terminals 6 and 6' to the signal output terminals 15 and 15' is is the following formula.

Here, if we set x=R/R6, e-ψ((")-Z(ω),' R6, equation (5) becomes It can be seen that the characteristic is added by 1.

It operates as a variable equalizer that can be changed.

〔Effect of the invention〕

As explained above, the present invention has the advantage that a variable equalizer (:r7) can be constructed using only one impedance element.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figures 2 and 3 are circuit diagrams showing one embodiment of the present invention.
The figure is a circuit diagram showing a conventional variable equalizer.

Claims (1)

[Claims] (1) The base of the first transistor and the ground are used as signal input terminals, the emitter of the first transistor and the base of the second transistor are connected via the first variable resistor, and the emitter of the first transistor is connected to the base of the second transistor through the first variable resistor. The base is grounded via an impedance element, the collector of the second transistor is grounded via a second variable resistor having a value equal to that of the first variable resistor, and is connected to the base of the third transistor. , further, the collector of the third transistor is grounded, the collector of the first transistor and the emitter of the third transistor are connected via the first fixed resistor, and the emitter of the second transistor is connected to the first fixed resistor. 1. A variable equalizer, characterized in that the equalizer is grounded via a second fixed resistor having a value equal to that of the equalizer, and the collector of the first transistor and the ground are used as signal output terminals.