JPH0514093A - Resistance ladder type graphic equalizer - Google Patents

Abstract

PURPOSE:To realize the resistance ladder type graphic equalizer in which shock noise caused at a change of a gain is reduced by the inexpensive method, deviation of the state at boosting and cutting is eliminated and increase in externally mounted components is prevented in the case of semiconductor circuit integration. CONSTITUTION:An analog switch 11 is inserted between termination of a resistance ladder section 7 and an inverting input terminal of a noninverting input amplifier 3 and each resistance ladder section 7 is turned on only in the moment when the section 7 is not in the connection state to the noninverting input amplifier 3 and switched to the connection state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic equalizer, and more particularly to a resistance ladder graphic equalizer which can be easily integrated into a semiconductor.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional resistance ladder type graphic equalizer. In the figure, 1 is an audio signal input terminal, 2 is a resistor required at the time of cutting (at the time of attenuation), 3 is a non-inverting input terminal whose non-inverting input terminal is connected to the audio signal input terminal 1 via the resistor 2. Amplifier,
4 is an audio signal output terminal connected to the output side of the non-inverting input amplifier 3, 5 is a bias resistor for the non-inverting input amplifier 3 provided between the audio signal input terminal 1 and the ground, and 6 is non-inverting A feedback resistor provided between the output terminal and the inverting input terminal of the input amplifier 3 is a plurality of boost and cut gain setting resistor ladder sections, each of which is a plurality of series-connected resistors and several resistors. The resistance value setting switch includes a transmission gate connected to a resistor, and the resistance value is variably set by turning on these setting switches. Further, 8a and 8b are cut and boost analog switches as a connecting means composed of a transmission gate. A pair of switches 8a and 8b are provided for each resistance ladder section 7, and one end is a non-inverting input. It is connected to the non-inverting input terminal and the inverting input terminal of the amplifier 3, respectively, and any one or two or more switches 8b are selected and turned on at the time of boosting (amplifying), and any one or two at the time of cutting. The above switch 8a is selected and turned on. Further, 9 is a resonance circuit section using a semiconductor inductor, which is connected to the end of each resistance ladder section 7, and 10 is provided between the end of each resistance ladder section 7 and the ground, and switches between the switches 8a and 8b. High resistance (eg 1M) to suppress shock noise generated during operation
It is a resistor for shock noise prevention of about Ω).

Next, the operation will be described. At the time of boosting, one of the boost switches 8b is turned on, and the resistor ladder unit 7 is connected to the inverting input terminal of the non-inverting amplifier 3 via the turned-on switch 8b. The gain and frequency band of the non-inverting input amplifier 3 at the time of boosting are determined by the resonance impedance of the resistance value and the inductance and capacitance of the resonance circuit unit 9 connected to the resistance ladder unit 7. On the other hand, at the time of cutting, one of the switches 8a for cutting is turned on, and the resistance ladder unit 7 is connected to and connected to the non-inverting input terminal of the non-inverting input amplifier 3 via the turned-on switch 8a. Resistance ladder section 7
The gain and frequency band of the non-inverting input amplifier 3 at the time of cutting are determined by the series resonance impedance due to the resistance value of 1 and the inductance and capacitance of the resonance circuit unit 9 connected to the resistance ladder unit 7. In this way, the audio signal input terminal 1 is formed by the combination of the switches 8a and 8b.
It becomes possible to give the input audio signal a certain specific frequency characteristic. By the way, switch 8
When a and 8b are turned on, since the potential of the resistance ladder unit 7 is a float potential, the potential of the non-inverting input amplifier 3 is instantaneously pulled to the float potential by turning on the switches 8a and 8b, thereby outputting the audio signal. Terminal 4
A big shock noise occurs. In order to suppress this shock noise, a resistor 1 with a high resistance value of about 1 MΩ
0 is inserted between the end of the resistance ladder 7 and the ground,
The difference between the potential of the resistance ladder unit 7 and the potential of the non-inverting input terminal of the amplifier 3 is reduced, and the shock noise when the switches 8a and 8b are turned on is reduced.

[0004]

The conventional resistance ladder type graphic equalizer is constructed as described above, and since the resistor 10 is always connected between the end of the resistance ladder section 7 and the ground, boosting and cutting are performed. There was a problem that the time gain deviated slightly. Also, these resistors 1
The resistance value of 0 is as large as 1 MΩ, and when the graphic equalizer of this kind is integrated, if the resistors 10 are integrated together, the number of chips will increase and the cost will increase. However, there is a problem in that the number of external parts increases because the carbon resistors are externally attached without changing.

The present invention has been made in order to solve the above-mentioned problems, and in the case of semiconductor integration, the cost increase is suppressed as much as possible and the shock noise generated at the time of switching between boost and cut is reduced and boosted. At the same time, it is an object to obtain a resistance ladder type graphic equalizer capable of suppressing a slight deviation of the gain at the time of cutting.

[0006]

A resistance ladder type graphic equalizer according to the present invention comprises a non-inverting input amplifier having a non-inverting input terminal connected to a signal input terminal, and a plurality of resistance ladder sections whose resistance values can be variably set. And connecting means for selectively connecting the starting end of each resistance ladder portion to either the inverting input terminal or the non-inverting input terminal of the non-inverting input amplifier,
Resonant circuit sections respectively connected to the ends of the resistance ladder sections, connected between the ends of the resistance ladder sections and the inverting input terminal of the non-inverting input amplifier, and the resistance ladder sections being the connecting means. It is provided with a switch that is turned on only during a transition period in which the non-connection state is switched to the connection state by the above, and holds the potential of each of the resistance ladder units at the same potential as the potential of the inverting input terminal of the non-inverting input amplifier. .

[0007]

According to the present invention, a shock noise preventing switch is connected between the end of each resistance ladder section and the inverting input terminal of the non-inverting input amplifier, and this switch is connected from the non-connection state of each resistance ladder section. It is turned on only during the transition period when it switches to the state. As a result, the potential of the resistance ladder section and the potential of the inverting input terminal of the non-inverting input amplifier are held at the same potential during the transition period, so that no sudden potential change occurs and shock noise is greatly suppressed. In addition, the gain deviation during boosting and cutting is suppressed. Further, it is not necessary to use a high resistance external resistor as in the conventional case.

[0008]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. Figure 1
FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and description thereof will be omitted. In this embodiment, a noise prevention analog switch 11 is connected between the non-inverting input terminal of the non-inverting input amplifier 3 and the end of each resistance ladder section 7. Then, the analog switch 11 is connected to the non-inverting input terminal and the inverting input terminal of the non-inverting input amplifier 3 by the switches 8a and 8b serving as connecting means, respectively. The part 7 has switches 8a and 8b.
Thus, the switch is turned on only at the moment of switching from the non-connected state to the connected state, and the potential of the non-inverting input terminal of the non-inverting input amplifier 3 and the potential of the terminal end of each resistance ladder unit 7 are held at the same potential. As the analog switch 11, it is preferable to use a switch having a long drain-source distance and a small width.

Next, the operation will be described with reference to FIG. When the switches 8a and 8b are off, the analog switch 11 is turned on so that the potential at the (termination) of the resistance ladder unit 7 is non-inverted input via the on resistance (up to several hundred KΩ) of the analog switch 11. The potential of the inverting input terminal of the amplifier 3 is the same as the potential of the input signal. Next, as shown in FIG. 2 (a), at the moment when the switches 8a and 8b change from the off state to the on state, the analog switch 11 remains held in the on state as shown in FIG. 2 (b), and the switches After 8a and 8b are completely turned on, the analog switch 11 is turned off as shown in FIG. 2 (b). As a result, even if the switches 8a and 8b are turned on, the potential at the terminal end, that is, the starting end of the resistance ladder unit 7 becomes the same potential as the input signal potential due to the action of the analog switch 11, so that no abrupt potential change occurs. Shock noise generated at the audio signal output terminal 4 can be reduced. In particular, when the switch 8b is turned on, the shock noise generated because the circuit is in the boost state is amplified by the non-inverting input amplifier 3 and becomes a particularly large shock noise in the audio signal output terminal 4 in the conventional example of FIG. However, in this embodiment, since the potential of the resistance ladder unit 7 and the potential of the inverting input terminal of the non-inverting input amplifier 3 are made the same potential by the analog switch 11 before the switch 8b is turned on, the shock generated during boosting It is possible to significantly reduce noise as compared with the conventional example. In addition, by turning off the analog switch 11 after the switches 8a and 8b are completely turned on, an extra resistance component is not added to the resistance ladder unit 7, and the gain deviation at the time of boosting and cutting is eliminated. It becomes possible.

[0010]

As described above, according to the present invention, a non-inverting input amplifier whose non-inverting input terminal is connected to a signal input terminal, and a plurality of resistance ladder sections whose resistance values can be set variably,
Connecting means for selectively connecting the starting end of each resistance ladder section to either the inverting input terminal or the non-inverting input terminal of the non-inverting input amplifier, and the resonance circuit section respectively connected to the terminal ends of the resistance ladder sections. Is connected between the end of each of the resistance ladder sections and the inverting input terminal of the non-inverting input amplifier, and is turned on only during a transitional period when the resistance ladder sections are switched from the non-connection state to the connection state by the connection means. , And a switch for holding the potential of each of the resistance ladder sections at the same potential as the potential of the inverting input terminal of the non-inverting input amplifier, so boosting and cutting can be performed while minimizing the cost increase in the case of semiconductor integration. It is possible to reduce the shock noise generated at the time of switching by an inexpensive method, eliminate the gain deviation at the time of boosting and cutting, and also to attach externally. There is an effect that it is possible to prevent the goods from becoming many.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a resistance ladder type graphic equalizer according to the present invention.

FIG. 2 is a timing diagram for explaining the operation of FIG.

FIG. 3 is a configuration diagram showing a conventional resistance ladder graphic equalizer.

[Explanation of symbols]

 3 Non-inverting input amplifier 7 Resistor ladder section 8 (a) Cut analog switch 8 (b) Boost analog switch 9 Resonance circuit section 11 Shock noise prevention analog switch

Claims (1)

Claims: 1. A non-inverting input amplifier, a non-inverting input terminal of which is connected to a signal input terminal, a plurality of resistance ladder sections whose resistance values can be variably set, and a starting end of each resistance ladder section. To a non-inverting input terminal or a non-inverting input terminal of the non-inverting input amplifier, a resonance circuit section connected to the end of each resistance ladder section, and each resistance ladder section. Connected between the terminating end of the non-inverting input amplifier and the inverting input terminal of the non-inverting input amplifier, and is turned on only during a transient period in which each of the resistance ladder sections is switched from the non-connection state to the connection state by the connecting means. A resistor ladder type graphic equalizer, characterized in that it comprises a switch for holding each potential at the same potential as that of the inverting input terminal of the non-inverting input amplifier.