JPH0566769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electronic volume circuit that can be used to adjust the volume and sound quality of consumer equipment.

Conventional configurations and their problems In recent years, in the field of consumer electronics, in order to respond to miniaturization and higher performance, electronic control using digital control technology has been implemented, and audio systems that are easier to use for consumers have been implemented. Systems are being developed.

Hereinafter, a conventional digitally controlled electronic volume circuit closely related to the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of a conventional digitally controlled electronic volume circuit. In FIG. 1, 1 is an input terminal, and 2 is an R-2R ladder resistor network. Reference numeral 3 denotes a switching circuit composed of, for example, a group of MOS type FET analog switches. Reference numeral 4 denotes an adder circuit composed of an operational amplifier and the like having a feedback resistor R _fB . Further, 5 is an output terminal.

The operation of the digitally controlled electronic volume circuit configured as described above will be described below. An input signal acting as a current source is input to an R-2R ladder resistor network 2. The output current obtained from each terminal of this R-2R ladder resistor network 2 is selected by a switching circuit 3 controlled by an external digital control signal, and then converted into a voltage by a next adding circuit 4. be done. The output current obtained from each terminal of the R-2R ladder resistor network 2 becomes half of the input current as the distance from the input terminal 1 increases. In other words, since the output current of the nth stage is (1/2) ⁿ of the input current, any amount of attenuation can be obtained by independently controlling each switch element included in the switching circuit 3.

However, in the above configuration, in order to obtain a desired amount of attenuation, a plurality of switch elements must be brought into conduction.
This has the problem that the digital control signal generation circuit for controlling the switching circuit 3 becomes complicated.

OBJECTS OF THE INVENTION An object of the present invention is to provide an electronic volume circuit that can be controlled by a simple digital control signal and that can provide arbitrary attenuation characteristics.

Structure of the Invention The electronic volume circuit of the present invention comprises an R-2R ladder that includes parallel resistors divided into appropriate ratios whose parallel resistance value is 2R to attenuate the level of an input signal to an arbitrary level. shaped resistance net;
It consists of a switching circuit that selects one of the outputs of this R-2R ladder resistor network using a digital control signal, and a buffer amplifier circuit that extracts a signal from the output of this switching circuit. It can be controlled by a digital control signal and any desired attenuation characteristic can be obtained.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows a configuration diagram of an electronic volume circuit according to an embodiment of the present invention. In FIG. 2, reference numeral 6 denotes an R-2R ladder resistor network in which two resistors R ₁ and R ₂ are connected in parallel, with the resistor 2R portion of the R-2R ladder resistor network divided at an appropriate ratio. In this case, 1/R ₁ +1/R ₂ = 1/2R. 7 is a switching circuit composed of, for example, a group of analog switches of MOS FETs, and 4 is an adder circuit composed of an operational amplifier circuit having a feedback resistor R _fB .

The operation of the electronic volume circuit of this embodiment configured as described above will be explained below. First, the input signal that operates as a current source is input to input terminal 1.
is inputted to the R-2R ladder resistor network 6. Originally, the output current obtained from each terminal of the R-2R ladder resistor network becomes half of the input current as the distance from the input terminal increases. In other words, the input current is
The input current is attenuated in steps of 6 dB, but the input current can be attenuated in arbitrary steps by connecting resistors divided at an appropriate ratio in parallel to the 2R resistor portion, as in the R-2R ladder resistor network 6. becomes possible.
For example, if the ratio is approximately 5:2, the input current will be attenuated in 3 dB steps. This R-2R
The output current of the ladder-shaped resistor network 6 is selected by a switching circuit 7 in which one set of switch elements is controlled by an external digital control signal, and after being converted into a voltage by the next adding circuit 4, It is output to output terminal 5. Therefore, by using an R-2R ladder resistor network containing parallel resistors divided into appropriate ratios, the entire electronic volume circuit
Attenuation in 3dB steps can be obtained.

As described above, according to this embodiment, by using the R-2R ladder resistor network 6 in which the resistors obtained by dividing the resistor 2R portion of the R-2R ladder resistor network at an appropriate ratio are connected in parallel, By controlling only one set of switch elements of the switching circuit 7, attenuation in 3 dB steps can be obtained, thereby simplifying the digital control signal.

In the above example, the input signal is attenuated in 3 dB steps in the R-2R ladder resistor network, but the attenuation step is not limited to 3 dB, and the input signal is attenuated in 3 dB steps. Any device may be used as long as it has the function of attenuating to an arbitrary value by connecting in parallel resistors whose parts are divided into a plurality of appropriate ratios. For example, by connecting three resistors in parallel, it is possible to achieve attenuation in 2dB steps, and it is not limited to a single step like 3dB steps.
Any device may be used as long as it has the function of obtaining an arbitrary attenuation characteristic by suitably changing the dividing ratio of the resistor 2R portion of the R-2R ladder resistor network and combining them.

Effects of the Invention As is clear from the above explanation, the present invention has R-
It is constructed with an R-2R ladder resistor network that can obtain any desired attenuation characteristic by connecting in parallel the resistors obtained by dividing the resistor 2R of the 2R ladder resistor network into an appropriate ratio. An excellent effect is obtained in that an electronic volume circuit can be controlled by a digital control signal that can be generated by a simple circuit, and has arbitrary attenuation characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional digitally controlled electronic volume circuit, and FIG. 2 is a block diagram of an electronic volume circuit according to an embodiment of the present invention. 1...Input terminal, 2, 6...R-2R ladder resistor network, 3, 7...Switching circuit, 4...Addition circuit, 5...Output terminal. However, Figures 1 and 2
Among the reference numerals indicating each part in the figure, the same reference numerals indicate that the parts have the same function.

Claims (1)

[Claims] 1. R-2R, which includes a parallel resistor divided into an appropriate ratio whose parallel resistance value is 2R, in order to attenuate the level of the input signal to an arbitrary level.
It consists of a ladder-shaped resistor network, a switching circuit that selects one of the outputs of this R-2R ladder-shaped resistor network using a digital control signal, and a buffer amplifier circuit that extracts a signal from the output of this switching circuit. Features an electronic volume circuit.