JPS5818761B2 - variable resistance device - Google Patents

Description

[Detailed description of the invention] The present invention changes the overall resistance value by operating the sliding terminal, and the output impedance seen from the output terminal to the input side remains constant regardless of the position of the sliding terminal. It was designed so that

Generally, in audio equipment such as a stereo, the

As shown in FIG. 1, an input audio signal applied to an input terminal 1 is applied to a variable resistor 2, and after adjusting the volume there, it is supplied to a tone amplifier 4 via an output terminal 3.

That is, the total resistance value between terminals a and b is R1, the resistance value between terminals a and 0, and between b and c is R1 and R2, respectively, the input signal voltage applied to input terminal 1 is Vin, and the input signal voltage applied to output terminal 3 is When the output signal voltage that appears is Vout, the volume is controlled by the following relationship.

On the other hand, the output impedance Zo (
Assuming that the impedance before the input terminal 1 is zero, the impedance seen from the output terminal 3 to the input side is expressed as follows, and its impedance characteristic curve is as shown in FIG.

That is, when R1=R/2, the output impedance is maximum at Zo=R/4), and when R1=0 and R1=R, the output impedance is minimum at z=o.

However, when the output impedance Zo fluctuates as the volume is adjusted in this way, the same wave number characteristics and distortion rate characteristics change accordingly, resulting in a problem that the reproduction performance of the audio device itself is impaired.

The present invention provides a variable resistance device that solves these conventional problems.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 3, parts with the same symbols as in FIG. 1 have the same functions.

5 is a variable resistance device consisting of first and second variable resistors 6 and 7; 8 is a center tap g of the second variable resistor 7;
This is the output terminal drawn out from here.

Both ends d and e of the second variable resistor 7 are open, and the sliding terminal f is connected to the sliding terminal C of the first variable resistor 6, and is slid together with the sliding terminal C. shall be

The total resistance value of the second variable resistor 7 is set to R/2.

In other words, it is set to % of the total resistance value R of the first variable resistor 6.

In the above configuration, by operating the sliding terminals c and f, the volume can be adjusted accordingly.

That is, similar to equation (1), RlV is applied to the sliding terminal C.
A divided voltage of in /(R, + R2) is taken out, and this voltage is further applied to the terminal f2g of the second variable resistor 7.
The voltage is divided by the resistance value R3 between them and the impedance after the output terminal 8, and the voltage is extracted.

Therefore, even in the case of FIG. 3, the volume adjustment function is maintained as is.

Next, the output impedance Z (ie, the impedance viewed from the output terminal 8 to the input side) will be considered.

The output impedance 2° viewed from the sliding terminal C to the input side is expressed by equation (2) as in FIG.

Therefore, the output impedance Z is expressed as.

But? If the resistance value between terminals f2g/R3 is set so that
It becomes constant at /4.

For this reason, the output impedance does not change even when the volume is adjusted, and the frequency characteristics and distortion characteristics do not change either. In this case, the resistance change characteristic curve of the second variable resistor 7 may be set as shown in FIG.

Note that the variable resistance device 5 may be configured with two variable resistors 6 and 7 that interlock with each other as shown in FIG.
As shown in the figure, two variable resistors 6, 7 may be formed coaxially, and two contacts provided on a sliding piece may be brought into sliding contact with each resistor 6, 7 at the same time.

The numbers and symbols shown in FIGS. 4 and 5 correspond to those in FIG. 3.

Furthermore, if the impedance z2 before input terminal 1 is not zero but R4, R1 in equation (3) can be replaced with (R1+R4), and in this case, the output impedance z1 is Z1=(R+R4). A variable resistance device whose resistance is constant at /4 can be obtained.

That is, R3 in this case is becomes.

The output impedance characteristic curve at this time is as shown in Figure 7, and the output impedance z1 is (R + R4)
In order to maintain the constant value of /4, the resistance change characteristic curve of the second variable resistor 7 should be set as shown in FIG.

In addition, in the embodiment, the second variable resistor is composed of one variable resistor, but it can be composed of two or more variable resistors, and the entire variable resistor device 5 is composed of three or more variable resistors. It goes without saying that similar effects can be obtained even if the structure is configured as follows.

As described above, according to the present invention, it is possible to construct a variable resistance device in which the output impedance always remains constant while changing the overall resistance value by operating the sliding terminal.

Therefore, when used as a volume for adjusting the volume of an audio device, the volume can be adjusted without changing the frequency characteristics or distortion characteristics.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional variable resistor, Fig. 2 is its output impedance characteristic diagram, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Figs. 4 and 5 are its specific details. FIG. 6 is a plan view showing a configuration example; FIG. 6 is a diagram showing a resistance change characteristic curve of the second variable resistor of the above embodiment; FIG. 7 is an output impedance characteristic diagram of another embodiment of the present invention; FIG. FIG. 2 is a diagram showing a resistance change characteristic curve of the second variable resistor of the embodiment included in the package. 1... Input terminal, 4... Tone amplifier, 5... Variable resistance device, 6... First variable resistor, 7... ...Second variable resistor, 8...
...Output terminal.

Claims (1)

[Claims] 1. A sliding terminal of a first variable resistor whose both ends are connected to a signal input terminal and a reference potential point, respectively, is connected to a sliding terminal of a second variable resistor whose both ends are open. Then, both the sliding terminals are operated in conjunction with each other, and an output signal is output from the output terminal provided on the second variable resistor. 2. A variable resistance device characterized in that by taking out the number, the output impedance as viewed from the output terminal to the input side becomes constant regardless of the positions of both the sliding terminals.