JP2005117489A - Electronic volume circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an electronic volume circuit in which a chip area is reduced by reducing a volume attenuation amount error and reducing the number of switches and the number of ladder resistors.
An electronic volume circuit includes a first-stage ladder volume unit having 15 ladders and switches, a second-stage ladder volume unit having six ladder resistors and switches, an input terminal, and an output. The terminal 5 is composed of a COM terminal 6 and an output load resistor RL. The first-stage ladder volume unit 2 and the second-stage ladder volume unit 3 are cascaded between the input terminal 4 and the output terminal 5, and the output load resistance RL is between the output terminal 5 and the COM terminal 6. The last ladder resistor R17b of the first ladder volume unit 2 and the last ladder resistor R25 of the second ladder volume unit 3 are connected to the COM terminal 6.
[Selection] Figure 1

Description

  The present invention relates to an electronic volume circuit in which a chip area is reduced by reducing a volume attenuation error and reducing the number of switches and ladder resistors.

  A resistance ladder type electronic volume circuit is frequently used for an electronic volume used in AV products such as minicomponents and TVs. As this type of electronic volume circuit, the one shown in FIG. 10 is known (for example, see Patent Document 1). FIG. 10 is a circuit configuration diagram showing an electronic volume circuit.

  As shown in FIG. 10, the electronic volume circuit 101 disclosed in Patent Document 1 includes a ladder volume unit 102 having 81 ladder resistors (R100 to R180) and 81 switches (S100 to S180), an input terminal 104, and an output. It consists of a terminal 105 and a COM terminal 106.

  The ladder volume unit 102 is provided between the input terminal 104 and the output terminal 105 and includes a plurality of switches that bridge the resistances connected in parallel and adjust the volume attenuation with a relatively small step width of 1 dB. ing. The last ladder resistor R180 is connected to a COM terminal 106, which is connected to the ground (analog ground) or 1/2 Vcc (high potential side power supply).

  The electronic volume circuit 101 is a circuit that turns on any one of the switches S100 to S180 of the ladder volume unit 102 and outputs a signal attenuated to a desired volume attenuation amount to the output terminal 105.

Here, all the switches are connected in series to the input of a buffer amplifier having a high input impedance (not shown), and the on-resistance of the switch is sufficiently smaller than the input impedance of this buffer amplifier, so that a good input / output interval is achieved. Gain and distortion characteristics can be obtained.
Japanese Patent Laid-Open No. 11-177371 (page 5, FIG. 3)

  In the electronic volume circuit described above, in order to adjust the volume attenuation with a relatively small step width of 1 dB, a plurality of switches and ladder resistors (each 81) are provided. Will increase. Therefore, there is a problem that the chip cost of the semiconductor integrated circuit incorporating the electronic volume circuit increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electronic volume circuit in which the chip area is reduced by reducing the volume attenuation error and reducing the number of switches and the number of ladder resistors. It is to provide.

In order to achieve the above object, an electronic volume circuit according to one embodiment of the present invention includes a small step by bridging an input terminal to which an input signal is input and a ladder resistor connected to the input terminal and connected in parallel. The first step ladder volume unit having a plurality of switches for adjusting the volume attenuation amount by the width, and the small step width by bridging the ladder resistor connected in parallel to the first step ladder volume unit. Connected to the second ladder volume section having a plurality of switches for adjusting the volume attenuation amount with a larger step width, and to the second ladder volume section, from the first and second ladder volume sections. An output terminal for inputting an output signal to be output, and the first-stage ladder volume unit and the second-stage ladder volume unit are connected to the input terminal. Are connected in cascade between the output terminals and turn on one of the switches of the first ladder volume section and turn on one of the switches of the second ladder volume section. Thus, an output signal attenuated to a desired volume attenuation amount is output.

  In order to achieve the above object, an electronic volume circuit according to another aspect of the present invention bridges an input terminal to which an input signal is input and a ladder resistor connected to the input terminal and connected in parallel. The first ladder volume section having a plurality of switches for adjusting the volume attenuation amount with a small step width, and the small ladder volume section connected to the first ladder volume section and connected in parallel to each other. A second-stage ladder volume section having a plurality of switches for adjusting the volume attenuation amount with a step width larger than the step width, and the first-stage and second-stage ladder volumes connected to the second-stage ladder volume section. The first and second slots connected in parallel to the output terminal for inputting the output signal output from the section and the ladder resistor at the final stage of the second ladder volume section. , A resistor connected to the first switch, a ladder resistor at the last stage of the ladder volume section of the first stage, the resistor, and a COM terminal connected to the second switch. The first-stage ladder volume section and the second-stage ladder volume section are cascaded between the input terminal and the output terminal, and the first switch and the resistor are connected to the second-stage ladder volume section. A cascade connection is made between the last ladder resistor of the volume section and the COM terminal, and one of the switches of the first ladder volume section is turned on, and the switch of the second ladder volume section is turned on. One of them is turned on, and an output signal attenuated to a desired volume attenuation amount is output by turning on one of the first or second switches. And butterflies.

  According to the present invention, it is possible to provide an electronic volume circuit in which the volume attenuation amount error is reduced and the number of switches and the number of ladder resistors are reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, an electronic volume circuit according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an electronic volume circuit.

  As shown in FIG. 1, the electronic volume circuit 1 has 15 ladder resistors (R10, R11a, R11b to R16b, R17a, R17b) and 15 switches (S10, S11a, S11b, S12a to S16b, S17a, S17b). First-stage ladder volume section 2, ladder resistance (R20, R21, R22 to R24, R25) and second-stage ladder volume section 3 each having six switches (S20, S21, S22 to S24, S25), input The terminal 4 is composed of an output terminal 5, a COM terminal 6, and an output load resistor RL.

  The first-stage ladder volume unit 2 and the second-stage ladder volume unit 3 are cascaded between the input terminal 4 and the output terminal 5, and the output load resistance RL is between the output terminal 5 and the COM terminal 6. The last ladder resistor R17b of the first ladder volume unit 2 and the last ladder resistor R25 of the second ladder volume unit 3 are connected to the COM terminal 6.

  The first-stage ladder volume unit 2 bridges the first-stage ladder resistance connected in parallel and adjusts the volume attenuation in the range of 0 dB to −7 dB with a relatively small step width. A plurality of switches are provided. Here, two resistors and two switches each having a different resistance value are provided in a 1 dB step width.

  On the other hand, the second-stage ladder volume unit 3 bridges the second-stage ladder resistor connected in parallel and adjusts the volume attenuation in the range of 0 dB to −40 dB with a relatively large 8 dB step width. A plurality of second-stage switches are provided.

  Here, the total resistance value of the first-stage ladder resistors (R10, R11a, R11b to R16b, R17a, R17b) is 20 KΩ, and the total of the second-stage ladder resistors (R20, R21, R22 to R24, R25). The resistance value is set to 50 KΩ, and the resistance value of the output load resistor RL is set to 100 KΩ.

  The electronic volume circuit 1 turns on one of the switches (S10, S11a, S11b, S12a to S16b, S17a, S17b) of the first-stage ladder volume section 2 to turn on the second-stage ladder volume section 3 In this circuit, one of the switches (S20, S21, S22 to S24, S25) is turned on to output a signal attenuated to a desired volume attenuation amount to the output terminal 5.

  Next, an equivalent circuit diagram of the electronic volume will be described. FIG. 2 is an equivalent circuit diagram of the electronic volume.

  As shown in FIG. 2, the electronic volume equivalent circuit 10 includes a first-stage ladder volume section 2 shown in FIG. 1 in which the first-stage first variable resistor R1 and the first-stage second variable resistor R2. The second-stage ladder volume unit 3 shown in FIG. 1 is represented by a second-stage first variable resistor R3 and a second-stage second variable resistor R4.

  The first variable resistor R1 at the first stage is connected to the input terminal 4, and the first variable resistor R3 at the second stage includes the first variable resistor R1 and the second variable resistor R2 at the first stage. The output terminal 5 is connected between the first variable resistor R3 at the second stage and the second variable resistor R4 at the second stage. The output load resistor RL is provided between the output terminal 5 and the COM terminal 6. The second variable resistor R2 at the first stage, the second variable resistor R4 at the second stage, the output load resistor RL, and the COM terminal 6 are grounded. Although the COM terminal 6 is grounded to the ground (ground) 7, it may be connected to 1/2 Vcc (high potential side power supply).

Here, the second stage total resistance (Rt2) composed of the second stage ladder resistance and the output load resistance RL is:
Rt2 = R3 + (R4 x RL) / (R4 + RL) ... (Equation 1)
It is represented by The total resistance value (Rt) composed of the first-stage ladder resistance, the second-stage ladder resistance, and the output load resistance RL is:
Rt = R1 + (R2 x Rt2) / (R2 + Rt2) ... (Equation 2)
It is represented by Subsequently, the volume attenuation ratio (Rtp1) of the ladder resistance in the first stage is
Rtp1 = (R2 x Rt2) / (R2 + Rt2) ... (Equation 3)
It is represented by On the other hand, the volume attenuation ratio (Rtp2) of the second ladder resistance is
Rtp2 = (R4 x RL) / (R4 x RL) ... (Equation 4)
It is represented by The volume attenuation amount (GV) at the output terminal 5 is the sum of the volume attenuation amount at the first stage and the volume attenuation amount at the second stage, and the volume attenuation amount (GV) is
GV = 20 x Log [(Rtp1 / Rt) x (Rtp2 / Rt2)] (Equation 5)
It is represented by

  Next, the relationship between the volume attenuation setting value of the electronic volume circuit and the volume attenuation error will be described. FIG. 3 is a characteristic diagram showing the relationship between the volume attenuation setting value of the electronic volume circuit 1 and the volume attenuation error. Here, the volume attenuation amount error can be obtained from the difference between the volume attenuation amount setting value and the volume attenuation amount (GV) expressed by Expression (5).

  As is apparent from this characteristic diagram, the volume attenuation amount error of the electronic volume circuit 1 has a maximum value when the volume attenuation amount setting value is −14 dB, but the value is as small as −0.068 dB, and the volume attenuation amount setting value. In the range of 0 to -8 dB and -16 to -47 dB, it is -0.01 dB or less. From this, it can be seen that the electronic volume circuit 1 has a good linearity characteristic in relation to the volume attenuation amount with respect to the volume attenuation amount setting value.

  As described above, in the electronic volume circuit of this embodiment, the first-stage ladder volume unit 2 that adjusts the volume attenuation amount with a relatively small step width between the input terminal 4 and the output terminal 5 and the relatively large 8 dB. The second-stage ladder volume unit 3 that adjusts the volume attenuation by the step width is connected in cascade, and the first-stage ladder volume unit 2 is provided with two ladder resistors and two switches having different resistance values in a 1 dB step width. In addition, since the two ladder resistors provided in the same step width have the lower resistance set larger than the upper resistance, the volume attenuation error with respect to the volume attenuation setting value can be reduced. .

  Furthermore, the number of ladder resistors and switches is reduced to ½ or less compared to an electronic volume circuit that adjusts the attenuation in a range of a 1 dB step width, which is a relatively small step width, with a single-stage ladder volume configuration. Therefore, the chip area of the electronic volume circuit can be reduced.

  Therefore, the volume attenuation amount error can be reduced, and the chip cost of the semiconductor integrated circuit incorporating the electronic volume circuit can be reduced.

  Next, an electronic volume circuit according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 4 is a circuit configuration diagram showing an electronic volume circuit.

  As shown in FIG. 4, the electronic volume circuit 1a includes seven ladder resistors (RX10, RX11, RX12 to R15, R16) and eight switches (SX10, SX11, SX12, SX13 to SX15, SX16, SX17). The first-stage ladder volume section 2a, the 13-stage ladder resistors (RY20, RY21 to RY32) and the 14-stage switches (SY20, SY21, SY22 to SY32, SY33), the second-stage ladder volume section 3a, and the input The terminal 4 includes an output terminal 5, a COM terminal 6, an output load resistor RL, switches S41 and S42, and a resistor Rz.

  The first-stage ladder volume unit 2a and the second-stage ladder volume unit 3a are connected in cascade between the input terminal 4 and the output terminal 5, and the switches S41 and S42 are connected to the second-stage ladder volume unit 3a. The last-stage ladder resistor RY32 and the COM terminal 6 are connected in parallel, and the switch S41 and the resistor Rz are cascade-connected between the last-stage ladder resistor RY32 and the COM terminal 6 of the second-stage ladder volume unit 3a. Yes. The ladder resistor RX16, resistor Rz, and switch S42 in the final stage of the first-stage ladder volume unit 2 are connected to the COM terminal 6.

  The first-stage ladder volume unit 2a bridges the first-stage ladder resistors connected in parallel to adjust the volume attenuation in the range of 0 dB to −7 dB with a relatively small 1 dB step width. A plurality of eye switches are provided.

  On the other hand, the second-stage ladder volume unit 3a is bridged with the second-stage ladder resistor connected in parallel to adjust the volume attenuation in the range of 0 dB to -95 dB with a relatively large 8 dB step width. A plurality of second-stage switches are provided.

  Here, the total resistance value of the first-stage ladder resistors (RX10, RX11, RX12 to R15, R16) is 20 KΩ, and the total resistance value of the second-stage ladder resistors (RY20, RY21 to RY32) is 50 KΩ. , Rz are set to 50 KΩ, and the output load resistor RL is set to 100 KΩ.

  This electronic volume circuit 1a turns on one of the switches (SX10, SX11, SX12, SX13 to SX15, SX16, SX17) of the first-stage ladder volume section 2a, and the second-stage ladder volume section 3a. One of the switches (SY20, SY21, SY22 to SY32, SY33) is turned on, and the switch S41 or S42 is turned on to output a signal attenuated to a desired volume attenuation amount to the output terminal 5. It is a circuit to make. When the switch S41 is turned on, the resistor Rz is connected to the second ladder volume unit 3a.

  Next, an equivalent circuit diagram of the electronic volume will be described. FIG. 5 is an equivalent circuit diagram of the electronic volume.

  As shown in FIG. 5, in the electronic volume circuit 10a, the first-stage ladder volume section 2a shown in FIG. 4 is represented by the first-stage first variable resistor R1 and the first-stage second variable resistor R2. The second-stage ladder volume section 3a shown in FIG. 4 is represented by the second-stage first variable resistor R3, the second-stage second variable resistor R4, and the resistor Rz.

  The first variable resistor R1 at the first stage is connected to the input terminal 4, and the first variable resistor R3 at the second stage includes the first variable resistor R1 and the second variable resistor R2 at the first stage. The second variable resistor R4 in the second stage is provided between the first variable resistor R3 and the resistor Rz in the second stage, and the output terminal 5 is the first variable in the second stage. It is connected between the resistor R3 and the second variable resistor R4 in the second stage. The output load resistor RL is provided between the output terminal 5 and the COM terminal 6. The first stage second variable resistor R2, resistor Rz, output load resistor RL, and COM terminal 6 are grounded. Although the COM terminal 6 is grounded to the ground (ground) 7, it may be connected to 1/2 Vcc (high potential side power supply).

Here, the total resistance (Rt2) of the second stage when the switch S42 is turned on can be expressed by Expression (1), but the total resistance (Rt2b) of the second stage when the switch S41 is turned on is
Rt2b = R3 + [(R4 + Rz) x RL] / (R4 + Rz + RL)] (Equation 6)
It is represented by

  Next, the relationship between the volume attenuation setting value of the electronic volume circuit and the volume attenuation error will be described. FIG. 6 is a characteristic diagram showing the relationship between the volume attenuation setting value of the electronic volume circuit and the volume attenuation error.

  As is apparent from this characteristic diagram, the volume attenuation amount error of the electronic volume circuit 1a has a maximum value when the volume attenuation amount setting value is −7 dB, but the value is as small as −0.075 dB. From this, it can be seen that the electronic volume circuit 1a has a good linearity characteristic in relation to the volume attenuation amount with respect to the volume attenuation amount setting value.

  As described above, in the electronic volume circuit of the present embodiment, the first-stage ladder volume unit 2a that adjusts the volume attenuation amount with a relatively small 1 dB step width between the input terminal 4 and the output terminal 5 and the relatively large volume. A second-stage ladder volume unit 3b that adjusts the volume attenuation with an 8 dB step width is connected in cascade, and a switch S41 is turned on / off between the ladder resistor RY32 and the COM terminal 6 of the second-stage ladder volume unit 3b. Since the selectable resistor Rz is provided, two types of resistance values of the variable resistor in the second stage can be set. Therefore, the volume attenuation amount error with respect to the volume attenuation amount setting value can be reduced.

  Furthermore, the number of ladder resistors and switches is reduced to 1/3 or less compared to an electronic volume circuit that adjusts the volume attenuation within the range of 1 dB step width, which is a relatively small step width, with a one-stage ladder volume configuration. Therefore, the chip area of the electronic volume circuit can be reduced as compared with the first embodiment.

  Therefore, the volume attenuation amount error can be reduced, and the chip cost of the semiconductor integrated circuit incorporating the electronic volume circuit can be reduced.

  Next, a semiconductor integrated circuit according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 7 is a circuit configuration diagram showing an electronic volume circuit.

  Hereinafter, in the present embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted, and only different components are described.

  As shown in FIG. 7, the electronic volume circuit 1b includes a first-stage ladder volume section 2a, a second-stage ladder volume section 3a, an input terminal 4, an output terminal 5, a COM terminal 6, and a first output load resistor RL1. , Second output load resistor RL2, switch S51, and switch S52.

  The first output load resistor RL1 is provided between the output terminal 5 and the second output load resistor RL2, and the switches S51 and S52 are connected in parallel between the first output load resistor RL1 and the COM terminal 6, The switch S52 operates reversely to the switch S51 (turns off when S51 is on and turns on when S51 is off). The first output load resistor RL1, the second output load resistor RL2, and the switch S51 are connected in cascade between the output terminal 5 and the COM terminal 6.

  Here, the switch S51 performs the same operation as the first switch S20 of the ladder volume unit 3a at the second stage. The resistance value of the first output load resistor RL1 is set to 100 KΩ, and the resistance value of the second output load resistor RL2 is set to 461 KΩ.

  The electronic volume circuit 1b turns on one of the switches (SX10, SX11, SX12, SX13 to SX15, SX16, SX17) of the first-stage ladder volume section 2a to turn on the second-stage ladder volume section 3a. Then, when the switch S20 is turned on, the output load resistance value is set to 561 KΩ, which is the sum of the first output load resistance RL1 and the second output load resistance RL2, and the switches (SY21, SY22 of the second-stage ladder volume unit 3a are set. When any one of ˜SY32 and SY33) is turned on, the output load resistance value is set to 100 KΩ (RL1) of the first output load resistance RL1 to be attenuated to a desired volume attenuation. This is a circuit for outputting a signal to the output terminal 5.

  Next, an equivalent circuit diagram of the electronic volume will be described. FIG. 8 is an equivalent circuit diagram of the electronic volume.

  As shown in FIG. 8, the electronic volume equivalent circuit 10b includes the first-stage ladder volume section 2a shown in FIG. 7 in the first-stage first variable resistor R1 and the first-stage second variable resistor R2. The second-stage ladder volume unit 3a shown in FIG. 7 is represented by a second-stage first variable resistor R3 and a second-stage second variable resistor R4. It is represented as a variable output load resistor RL3 from which a value (100 KΩ or 561 KΩ) can be selected.

  The variable output load resistor RL 3 is provided between the output terminal 5 and the COM terminal 6 and is grounded to the ground (ground) 7.

  Next, the relationship between the volume attenuation setting value of the electronic volume circuit and the volume attenuation error will be described. FIG. 9 is a characteristic diagram showing the relationship between the volume attenuation setting value of the electronic volume circuit and the volume attenuation error.

  As is apparent from this characteristic diagram, the volume attenuation amount error of the electronic volume circuit 1b has a maximum value when the volume attenuation amount setting value is −103 dB, but the value is as small as −0.070 dB. In the range of 0 to −16 dB, it is −0.01 dB or less. From this, it can be seen that the electronic volume circuit 1b has a good linearity characteristic in relation to the volume attenuation amount with respect to the volume attenuation amount setting value.

  As described above, in the electronic volume circuit of the present embodiment, the first-stage ladder volume unit 2a that adjusts the volume attenuation amount with a relatively small 1 dB step width between the input terminal 4 and the output terminal 5 and the relatively large volume. A second-stage ladder volume unit 3b that adjusts the volume attenuation with an 8 dB step width is connected in cascade, and a second output that can be selected between the first output load resistor RL1 and the COM terminal 6 by turning on / off the switch S20. Since the output load resistor RL2 is provided, the output load resistor can be changed to a variable output load resistor RL3 that can set two types of resistance values. Accordingly, the output load resistance with respect to the output load resistance can be reduced with respect to the set value of attenuation.

  Furthermore, the ladder resistance and the number of switches are the same as in the second embodiment, compared to an electronic volume circuit that adjusts the volume attenuation within a range of 1 dB step width, which is a relatively small step width, with a single-stage ladder volume configuration. Since it can be reduced to 1/3 or less, the chip area of the electronic volume circuit can be reduced as compared with the first embodiment.

  Therefore, the volume attenuation amount error can be reduced, and the chip cost of the semiconductor integrated circuit incorporating the electronic volume circuit can be reduced.

  The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the invention.

  For example, in this embodiment, the volume attenuation amount of the second ladder volume section is adjusted with an 8 dB step width having a relatively large step width, but may be adjusted to another step width.

  Furthermore, the volume attenuation amount of the first and second ladder volume units may be adjusted with different step widths as appropriate depending on the required volume attenuation amount error.

1 is a circuit configuration diagram showing an electronic volume circuit according to Embodiment 1 of the present invention. 2 is an equivalent circuit of an electronic volume according to the first embodiment of the present invention. The characteristic view which shows the relationship between the volume attenuation amount setting value of the electronic volume concerning Example 1 of this invention, and a volume attenuation amount error. FIG. 6 is a circuit configuration diagram showing an electronic volume circuit according to a second embodiment of the present invention. 7 is an equivalent circuit of an electronic volume according to a second embodiment of the present invention. The characteristic view which shows the relationship between the volume attenuation amount setting value of the electronic volume concerning Example 2 of this invention, and a volume attenuation amount error. FIG. 6 is a circuit configuration diagram showing an electronic volume circuit according to a third embodiment of the present invention. The equivalent circuit of the electronic volume concerning Example 3 of this invention. The characteristic view which shows the relationship between the volume attenuation amount setting value of the electronic volume concerning Example 3 of this invention, and a volume attenuation amount error. The circuit block diagram which shows the conventional electronic volume circuit.

Explanation of symbols

1, 1a, 1b, 101 Electronic volume circuit 2, 2a First-stage ladder volume section 3, 3a Second-stage ladder volume section 4, 104 Input terminal 5, 105 Output terminal 6, 106 COM terminal 7 Ground (ground)
8 Attenuation amount due to first-stage volume 9 Attenuation amount due to second-stage volume 10, 10a, 10b Electronic volume equivalent circuit 102 Ladder volume section R1 First-stage first variable resistor R2 First-stage second resistance Variable resistor R3 Second stage first variable resistor R4 Second stage second variable resistor R10, R11a, R11b, R16b, R17a, R17b, RX10, RX11, RX12, RX15, RX16 First stage ladder resistor R20 R21, R24, R25, RX20, RX21, RX32 Second-stage ladder resistors R100, R101, R102, R178, R179, R180 Ladder resistors RL Output load resistors RL1 First output load resistors RL2 Second output load resistors RL3 Variable output load resistor Rz resistors S10, S11a, S11b, S12a, S16b, S17 a, S17b, SX10, SX11, SX12, SX13, SX15, SX16, SX17 First stage switches S20, S21, S22, S24, S25, SY20, SY21, SY22, SY32, SY33 Second stage switches S41, S42, S51, S52, S100, S101, S102, S103, S178, S179, S180 switch

Claims (9)

An input terminal to which an input signal is input;
A first-stage ladder volume unit having a plurality of switches connected to the input terminal and adjusting a volume attenuation amount with a small step width by bridging ladder resistors connected in parallel;
A second-stage ladder volume having a plurality of switches connected to the first-stage ladder volume section and adjusting a volume attenuation amount with a step width larger than the small step width by bridging ladder resistors connected in parallel. And
An output terminal that is connected to the second-stage ladder volume unit and that receives an output signal output from the first-stage and second-stage ladder volume units;
Comprising
The first-stage ladder volume section and the second-stage ladder volume section are cascade-connected between the input terminal and the output terminal, and any one of the switches of the first-stage ladder volume section is connected. An electronic volume circuit which outputs an output signal attenuated to a desired volume attenuation amount by turning on and turning on any one of the switches of the second ladder volume section.   The first-stage ladder volume section has a plurality of ladder resistors and switches having different resistance values in a 1 dB step width, and the second-stage ladder volume section has a volume attenuation with a step width larger than the 1 dB step width. 2. The electronic volume circuit according to claim 1, wherein the electronic volume circuit is adjusted.   The output load resistance is provided between the output terminal and the COM terminal, and this COM terminal is connected to the last stage ladder resistance of the first and second ladder volume units, and is connected to ground or ½ high. 4. The electronic volume circuit according to claim 2, wherein the electronic volume circuit is terminated with a potential-side power source. An input terminal to which an input signal is input;
A first-stage ladder volume unit having a plurality of switches connected to the input terminal and adjusting a volume attenuation amount with a small step width by bridging ladder resistors connected in parallel;
A second-stage ladder volume having a plurality of switches connected to the first-stage ladder volume section and adjusting a volume attenuation amount with a step width larger than the small step width by bridging ladder resistors connected in parallel. And
An output terminal that is connected to the second-stage ladder volume unit and that receives an output signal output from the first-stage and second-stage ladder volume units;
A first switch and a second switch connected in parallel to the last ladder resistor of the second ladder volume;
A resistor connected to the first switch;
A COM terminal connected to the last stage ladder resistance of the first stage ladder volume section, the resistance, and the second switch;
Comprising
The first-stage ladder volume section and the second-stage ladder volume section are cascade-connected between the input terminal and the output terminal, and the first switch and the resistor are connected to the second-stage ladder volume section. Is connected in cascade between the last stage ladder resistor and the COM terminal, and turns on one of the switches of the first ladder volume section, and among the switches of the second ladder volume section An electronic volume circuit that outputs an output signal attenuated to a desired volume attenuation amount by turning on any one and turning on either one of the first or second switches.   The first-stage ladder volume unit adjusts the volume attenuation by a 1 dB step width, and the second-stage ladder volume unit adjusts the volume attenuation by a step width larger than the 1 dB step width. The electronic volume circuit according to claim 4.   6. The electron according to claim 4, wherein an output load resistor is provided between the output terminal and the COM terminal, and the COM terminal is terminated to ground or a ½ high potential side power source. Volume circuit. An input terminal to which an input signal is input;
A first-stage ladder volume unit having a plurality of switches connected to the input terminal and adjusting a volume attenuation amount with a small step width by bridging ladder resistors connected in parallel;
A second-stage ladder volume having a plurality of switches connected to the first-stage ladder volume section and adjusting a volume attenuation amount with a step width larger than the small step width by bridging ladder resistors connected in parallel. And
An output terminal that is connected to the second-stage ladder volume unit and that receives an output signal output from the first-stage and second-stage ladder volume units;
A first output load resistor connected to the output terminal;
A second output load resistor connected to the first output load resistor;
A first switch connected to the second output load resistor and performing the same operation as the first switch of the second ladder volume;
A second switch connected between the first output load resistor and the second output load resistor;
A last stage ladder resistance of the first and second ladder volume sections, the first switch, and a COM terminal connected to the second switch;
Comprising
The first-stage ladder volume section and the second-stage ladder volume section are cascade-connected between the input terminal and the output terminal, and the first output load resistance, the second output load resistance, and The first switch is connected in cascade between the output terminal and the COM terminal, and the first and second switches are connected in parallel between the first output load resistor and the COM terminal. Turn on one of the switches of the ladder volume section of the second stage, turn on one of the switches of the ladder volume section of the second stage, and either one of the first or second switch An electronic volume circuit which outputs an output signal attenuated to a desired volume attenuation amount by turning on the signal.   The first-stage ladder volume unit adjusts the volume attenuation by a 1 dB step width, and the second-stage ladder volume unit adjusts the volume attenuation by a step width larger than the 1 dB step width. The electronic volume circuit according to claim 7.   9. The electronic volume circuit according to claim 7, wherein the COM terminal is terminated to ground or a 1/2 high potential side power source.

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