JPS6011602Y2 - variable attenuator - Google Patents

Description

[Detailed description of the invention] The present invention relates to a variable attenuator, and its purpose is to provide a variable attenuator that has a relatively low resistance value and can obtain a large maximum attenuation amount by improving the circuit pattern. There is something to do.

For example, in a type of variable attenuator whose total resistance value is relatively low, IKΩ, if you want to lower its maximum attenuation to about -120dB, the resistance between the input terminal and output terminal should be IKΩ.
It must be less than 1 mΩ, which is 7Ω.

However, when an electrode is conventionally formed by printing or spraying, and a terminal made of brass or iron plated with gold or silver is attached to this, a contact resistance of several milliohms occurs just at the contact area, which reaches a maximum. There was a drawback that the amount of attenuation could not be as large as expected.

The present invention solves the above-mentioned drawbacks by increasing the maximum attenuation of the variable attenuator by improving the circuit pattern.An embodiment is shown in the drawings and will be explained in detail below. A ground terminal connected to one end of the arc-shaped resistor 4, 2 an output terminal connected to the collector 5 through an electrode 2a inside the resistor 4, and 3 the other end of the resistor 4 via an electrode 3a. The input terminals 9 and 10 are sliders connected to the resistor 4 and the collector 5 in the direction of the arrow, that is, from the input terminal side to the ground terminal side, thereby guiding the voltage attenuated by the resistor 4 to the output terminal 2. , 6 are conductive parts for electrically connecting the slider 9 to the output terminal 2 via the resistor 7 when the slider 10 is located on the electrode 1a.

The feature of the present invention is that when the sliders 9 and 10 reach the ground side sliding end position, as shown in the enlarged view of the main part in Figure 1,
The outer slider 10 is on the electrode 1a connected to the earth terminal 1, and the inner slider 9 is on the conductive part 6 separated from the collector 5, so that the conductive part 6 is required. If it is, it means that it is connected to the output terminal 2 side via a fixed resistor 7 having a predetermined resistance value that can be trimmed, and this is connected to the output terminal 2 side.
According to the circuit diagram in the figure, the slider 9.1 shown in solid line
0 slides on the resistor 4 and collector 5 in the direction of arrow A and is at the position of the sliders 9 and 10 shown by dotted lines, the ground terminal 1 and the output terminal 2 are connected to the fixed resistor shown in Figure 1. They are electrically connected via 7.

RL is a load, r, which is an external circuit connected to output terminal 2;
2 is the number of meters generated when the ground terminal 1 and silver electrode 1a are squeezed
The contact resistance is Ω.

A voltage obtained by further dividing the voltage divided by the resistor 4 and the contact resistance r2 by the input impedance of the resistor 7 and the load RL appears at the output terminal 2, and the voltage value of the output terminal 2 is made equal to the input. To obtain a value that is 12ωB lower, set the resistance value of fixed resistor 7 to a value that is one digit larger than the input impedance value of load RL (
For example, when the input impedance is IKΩ, the fixed resistor 7 should be IOKΩ.

That is, in order to obtain an attenuation of -120 dB, the slider 9
It is the voltage obtained by dividing the voltage of .

Note that by arranging the collector 5 and the conductive part 6 to face each other in an L-shape, a slider 9 having two contact parts can be formed.
will always come into contact with the collector 5 or the conductive part 6, and since the output terminal 2 will always be connected to the ground terminal 1 via the sliders 9 and 10, the output terminal 2 will not be in an insulated state, and the output terminal It is possible to prevent noise from being mixed in from 2.

As shown above, in the conventional variable attenuator, since there is no fixed resistor 7 or conductive part 6 as in the present invention, a voltage corresponding to the resistance value of the contact resistance 2 generated at the contact part on the ground terminal 1 side is generated. appears as it is on the output terminal 2 side, and it was not possible to bring the potential at the sliding end position of the slider close to the ground potential.However, according to the present invention, the potential at the sliding end position of the slider cannot be brought close to the ground potential. By connecting a fixed resistor 7 with a certain resistance value to the output terminal 2, and connecting the earth terminal 1 and the output terminal 2 with the sliders 9 and 10, the potential appearing at the output terminal 2 is equal to that of the fixed resistor 7. It is determined by the product of the current flowing through the load RL and the resistance of the load RL, and the result is a value that is inversely proportional to the resistance value of the fixed resistor 7, which is the product of the voltage applied to the input terminal 3 and the resistance. By setting the voltage on the ground terminal 1 side attenuated by the body 4 and the resistance value of the load RL and the resistance value of the measuring resistor 7 connected to the output terminal 2 to desired values in advance, the contact portion of the ground terminal 1 can be Even if there is a contact resistance r2 of No need to enlarge the configuration, just output terminal 2
By simply providing the fixed resistor 7 having a predetermined resistance value depending on the load RL connected to the load RL, the above-mentioned effects can be obtained, and extremely great practical effects such as extremely good workability are achieved.

[Brief explanation of the drawing]

The drawings are all of the present invention, and FIG. 1A is a plan view of the circuit pattern, 0 is an explanatory view of the main part, and FIG. 2 is a circuit diagram. 1... Earth terminal, 2... Output terminal,
3... Input terminal, la, 2a, 3a...
...Electrode, 4...Resistor, 5...
Collector, 6... Conductive part, 7... Fixed resistor, 9, 10... Slider.

Claims (1)

[Scope of utility model registration request] A collector is formed on an insulating substrate, one end of which connects to the output terminal, and a resistor is formed outside of the collector, one end of which connects to the input terminal and the other end of which connects to the ground terminal. In a variable attenuator in which a slider slides on the resistor,
A conductive part separate from the collector is provided at the end of the collector, a specific resistor having a predetermined resistance value is interposed between the conductive part and the output terminal, and a plurality of conductive parts are provided on the part that slides on the slider collector. 1. A variable attenuator, characterized in that the contact portion is in contact with the collector or the conductive portion so that the output terminal is not in an insulated state.