JP2010068262A - Electronic volume - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic volume which is free of waveform distortion according to the magnitude of amplitude without upsizing a semiconductor element constituting a switch. <P>SOLUTION: The electronic volume includes: at least one first resistor connected to a signal input terminal in series; n resistors connected in series between the other end of the first resistor and a reference potential, wherein the other end of the first resistor is connected to output terminals; and n switches in which one ends are each connected to connection points of the n resistors, and the other ends are connected to the reference potential. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resistance ladder type electronic volume, and more particularly, to an electronic volume that reduces distortion at the time of switching a switch, reduces switching noise, and the like.

  FIG. 8 shows a conventional electronic volume circuit. As a conventional electronic volume, there is a circuit having a configuration employing a weighting method. In FIG. 8, IN is a signal input terminal, R1 to R10 are resistors, S1 to S10 are switches, 5 is an output buffer having a voltage follower configuration, and OUT is a signal output terminal.

In the electronic volume shown in FIG. 8, when any one of the switches S1 to S4 is selected and turned on, the resistance group of the resistors R1 to R4 is set to the resistance value of the 1 dB step configuration, and the attenuation is 0 to -3 dB. Quantity can be realized. Further, by selecting and turning on any one of the switches S5 to S10, when the resistance group of the resistors R5 to R10 is set to a resistance value of a 4 dB step configuration, an attenuation amount of −4 to −20 dB is realized. Can do. Therefore, by turning on any one of the switches S1 to S4 and any one of the switches S5 to S10, an attenuation amount of 0 to −23 dB is realized in 1 dB steps. Can do. For example, Patent Document 1 discloses such a weighting type electronic volume.
JP 11-177371 A

  In the electronic volume shown in FIG. 8, when the switch S1 and the switch S5 are turned on to realize the attenuation of 0 dB, the output buffer 5 connected to the switch S5 has a large input impedance and no current flows. r5 has no effect. However, since the switch S1 is connected to the resistors R5 to R10, a current flows through the switch S1, and the on-resistance r1 of the switch S1 affects the resistance voltage dividing ratio, which is different from the attenuation determined by the resistors R5 to R10. Attenuation amount.

  In addition, since the current varies with the input amplitude and the on-resistance r1 of the switch S1 varies, the waveform distortion also increases as a result of the amplitude. Similarly, when the switches S2 to S4 are selected, the amount of attenuation is determined by the partial pressure of the resistors R5 to R10, so that waveform distortion occurs. Thus, in order to reduce the on-resistance of the switches S1 to S4 in the previous stage and reduce the influence of the waveform distortion, it is necessary to increase the size of the MOS transistor or the like constituting the switch, and the electronic volume is increased. was there.

  An object of the present invention is to provide an electronic volume which solves the above-mentioned problems without solving the above-mentioned problems and without increasing the size of a semiconductor element constituting the switch.

  In order to achieve the above object, according to the first aspect of the present invention, at least one first resistor connected in series to a signal input terminal and the other end of the first resistor are connected to an output terminal. In addition, n resistors connected in series between the other end and a reference potential, and one end connected to each connection point of the n resistors, and the other end connected to the reference potential And n switches.

  The invention according to claim 2 of the present application is the electronic volume according to claim 1, wherein m resistors connected in series between a connection point between the first resistor and the output terminal and the reference voltage. And m switches having one end connected to each connection point of the m resistors and the other end connected to the reference potential.

  The invention according to Claim 3 of the present application is the electronic volume according to any one of Claims 1 and 2, wherein each of the n resistors is connected between the connection points of the n resistors and the n switches, or the m switches. A separate resistor is provided between each connection point of the resistor and the m switches.

  The invention according to claim 4 of the present application is the electronic volume according to any one of claims 1 to 3, wherein the switch is configured by a MOS transistor.

  In the present invention, one end of a changeover switch for setting an attenuation amount is commonly connected at a reference potential, thereby reducing the voltage applied to both ends of the switch and reducing the influence on the distortion due to the voltage dependency of the switch. it can. Accordingly, the switch can be miniaturized and the parasitic capacitance can be reduced, so that switching noise can also be reduced. In particular, when the changeover switch is composed of MOS transistors, the waveform distortion that occurs can be reduced, and the changeover noise can be reduced. Compared with the electronic volume shown in FIG. 8 described in the above-mentioned conventional example, this can reduce the waveform distortion and switching noise without increasing the area of the MOS transistor. This is very advantageous in terms of cost performance.

  FIG. 1 is a block diagram for explaining the principle of the electronic volume of the present invention. In FIG. 1, 1 is a signal input terminal, 2 is a signal output terminal, 3 is a reference potential, R (0) to R (n) are resistors, and S (1) to S (n) are switches.

  As shown in FIG. 1, the electronic volume of the present invention has a resistor R (0) connected in series between a signal input terminal 1 and a signal output terminal 2, and a connection point between the resistor R (0) and the signal output terminal 2. N resistors R (1) to R (n) are connected in series between the reference potential 3 and the reference potential 3. The n switches S (1) to S (n) are connected between the connection points of the resistors R (1) to R (n) and the reference potential 3.

  With this configuration, when a signal is input to the signal input terminal 1, the signal level of the input side of the switches S1 to S (n) is attenuated by the resistors R (0) to R (n-1). The output side of the switches S (1) to S (n) is connected to the reference potential 3, so that the potential difference generated between the switches is reduced. As a result, waveform distortion can be greatly reduced.

  Further, when the switches (1) to S (n) are changed from the on state to the off state, switching noise is generated on the input side of the switches (1) to S (n), and this switching noise is left on the output side as it is. Is transmitted. The switching noise is recognized as unpleasant noise by humans. In the present invention, the switching noise generated on the input side of the switches S (1) to S (n) is the resistance R (1) to R. Reduced by (n). As a result, when the attenuation amount is gradually increased from the switches S (1) to S (n), the switching noise is also reduced according to the attenuation amount, so that a great effect can be expected for the reduction of the switching noise. . Examples of the present invention will be described in detail below.

  FIG. 2 shows an electronic volume according to the first embodiment of the present invention. A resistor R1 is connected in series between the signal input terminal and the signal output terminal, and resistors R2 to R6 are connected in series between the connection point of the resistor R1 and the signal output terminal 2 and the reference potential. The switches S1 to S5 are connected between the connection points of the resistors R2 to R6 and the reference potential 3. The resistor R7 corresponds to an impedance connected to the output terminal.

  In the present embodiment, any one of the switches S1 to S5 is turned on, and the attenuation amount is set. A signal is input from the signal input terminal 1, and the signal level is attenuated by the resistor R1, the corresponding resistors R2 to R6, and the resistor R7 on the input side of the switch in the ON state. Specifically, when the switch S1 is in an on state, the signal level is attenuated by the resistors 1 to 7, and when the switch S5 is in an on state, the signal level is attenuated by the resistors R1, R2 and the resistor R7.

  In this embodiment, since the output side of the switch is connected to the reference potential, the potential difference generated between the switches is reduced. Specifically, when this switch is formed of a MOS transistor, when the input level or the potential difference between the switches is small, the on-resistance of the MOS transistor is less fluctuated and can be handled as a resistor exhibiting normal linear characteristics. Compared with the case where the conventional switch is composed of MOS transistors, the waveform distortion can be greatly reduced even if MOS transistors of the same size are used.

  Further, when the switch is changed from the on state to the off state, switching noise is generated from the input side of the switches S1 to S5, and when this switching noise is transmitted to the output as it is, it is recognized as unpleasant noise by humans. However, at this time, the switching noise generated on the input side of the switches S1 to S5 is reduced by the resistance division of the resistors R2 to R6 and the resistor R7 connected to the subsequent stage. For this reason, when the attenuation amount is gradually increased from S1 to S5, the switching noise is also reduced by resistance division according to the attenuation amount, so that a great effect can be expected for the reduction of the switching noise.

  Similarly, FIG. 3 shows a second embodiment of the present invention. In FIG. 3, R1 to R11 are resistors, and S1 to S9 are switches. In this embodiment, two circuits connected in parallel are connected in parallel, each of a plurality of resistors connected in series described in the first embodiment and a plurality of switches connected between the respective connection points and a reference potential. It has become the composition. Note that FIG. 3 illustrates an example in which the number of resistors connected in series is one less than in the case of FIG.

  FIG. 4 shows a third embodiment of the present invention. In FIG. 4, R1 to R10 are resistors, and S1 to S9 are switches. In this embodiment, the switches R6 to S9 are connected between the resistors R2 to R6 described in the first embodiment and their connection points and output terminals (not shown).

  Furthermore, as shown in FIGS. 5 and 6, various circuit configurations can be employed without departing from the principle of the present invention.

It is a basic block diagram of the electronic volume of the present invention. It is a concrete circuit diagram at the time of use of FIG. It is a concrete circuit diagram at the time of use of FIG. It is a concrete circuit diagram at the time of use of FIG. It is a circuit diagram of a specific electronic volume. It is a circuit diagram of the electronic volume of another specific example. It is a circuit diagram of the electronic volume of another specific example. It is a circuit diagram of the conventional electronic volume.

Explanation of symbols

1; signal input terminal, 2; signal output terminal, 3; reference potential, 5; output buffer, R1 to R26; resistor, S1 to S21; switch

Claims (4)

At least one first resistor connected in series to the signal input terminal;
The other end of the first resistor is connected to the output terminal, and n resistors connected in series between the other end and a reference potential;
An electronic volume, comprising: n switches having one end connected to each connection point of the n resistors and the other end connected to the reference potential.   M resistors connected in series between a connection point between the first resistor and the output terminal and the reference voltage, and one end connected to each connection point of the m resistors, 2. The electronic volume according to claim 1, further comprising m switches whose other ends are connected to the reference potential.   A separate resistor is connected between each connection point of the n resistors and the n switches, or between each connection point of the m resistors and the m switches. The electronic volume according to claim 1, wherein the electronic volume is provided.   4. The electronic volume according to claim 1, wherein the switch is constituted by a MOS transistor.

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