JP2000261298A - Analog switch circuit and multiplexer and demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an analog switch circuit reduced in a circuit scale without degrading performance by providing a synthesizing means which inverts one of the outputs of first and second switches, and synthesizes those outputs. SOLUTION: An analog input signal j is switched by a switch 12 according to a switch switching signal q from the outside part. The 0 level of the analog signal is inputted to a switch 13, and a switching operation is executed according to the switch switching signal q. Not only a switched signal k but also a switch switching leakage signal s are generated from the output of the switch 12, and only a switch switching leakage signal s' is generated from the output of the switch 13 according to those switching operations. Those switch switching leakage signals s and s' are both obtained according to the switch switching signal q so that the correlation can be made strong. Therefore, they are inverted and synthesized by an inverter/synthesizer 14 so that the switch switching leakage signal s can be almost canceled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog switch circuit and a multiplexer and a demultiplexer using the same, and more particularly to an analog switch circuit capable of switching without deteriorating the quality of an analog signal, and a multiplexer and a demultiplexer using the same. It is about.

[0002]

2. Description of the Related Art An analog switch circuit is a switch circuit for turning on / off an input analog signal and outputting the signal. FIG. 3 shows a configuration example of a multiplexer configured by using two analog switch circuits. The analog switch circuits 31 and 32 are provided with switching signals SW1 and SW2 shown in FIG.
The input analog signals S1 and S2 are alternately turned on by the switch SW2 and sent to the combiner 33, where they are combined to obtain an output analog signal SO. This multiplexer can be similarly configured with three or more input signals, and is used when a plurality of analog signals are switched in a time-division manner and are signaled by one common circuit.

FIG. 4 shows an analog switch circuit having two switches.
2 shows an example of a configuration of a demultiplexer configured by using a plurality of analog switches. Analog switch circuits 41 and 42 are also turned on alternately by switching signals SW1 and SW2 shown in FIG.
The input signal S from the distributor 43 is output to outputs SO1 and S1, respectively.
Output as O2. This demultiplexer can also be configured to divide one signal S into three or more, and is used to divide the signal S that is synthesized in a time-division manner.

In an analog switch circuit used for such a purpose, a switch switching signal leaks to an output side when a switch is switched, and the quality of an output analog signal may be degraded. To cope with this, an analog switch circuit equipped with a switch switching leakage signal canceling circuit has been developed, and a conventional configuration example is shown in a block diagram of FIG. In this circuit, the analog input signal a is inverted and distributed by the inverting distributor 51 into the input and the in-phase signal b and the inverted signal c. However, in the figure, one pulse is shown as an isolated waveform although the waveform actually exists continuously before and after. This in-phase signal b and inverted signal c
Are switched by switches 52 and 53, respectively. At this time, not only the switched signals d and e, but also switch switching leakage signals f and f 'are generated at the outputs of the switches 52 and 53, respectively. However, since these are both based on the external switch switching signal g, the correlation between the switch switching leakage signals f and f 'becomes very high. Therefore, by inverting and synthesizing these in the inverting synthesizer 54, the switch switching leakage signals f and f 'are almost canceled. On the other hand, in the inverting synthesizer 54, the signal d obtained by switching the in-phase signal b from the inverting distributor 51 has the same phase, and the signal e obtained by switching the inverted signal c is inverted and synthesized. , Analog input signal a
Becomes the same phase.

[0005]

As described above, by using the analog switch circuit shown in FIG. 5, it is possible to suppress the quality deterioration due to the leakage signal generated at the time of switching. However, this circuit configuration requires an inverting distributor and an inverting combiner in addition to the two switches, and has a problem that the hardware scale becomes large.

It is an object of the present invention to provide an analog switch circuit in which the circuit for canceling the conventional switch switching leakage signal is improved to reduce the circuit scale without deteriorating the performance.

[0007]

According to the present invention, an analog signal is input to an input terminal thereof, and when an external switching signal instructs on, the input analog signal is passed and output. When the switching signal indicates OFF, the first operation is performed so as not to output the input fanalog signal.
And the input terminal of the switch, the value of the 0 level of the analog signal is input as an input signal, and when the switch signal indicates ON, the input signal is output as it is,
When the switching signal indicates OFF, a second switch that operates so as not to output the input signal, and either one of the output of the first switch and the output of the second switch are inverted. And a synthesizing means for synthesizing the analog circuit.

Further, the present invention provides a plurality of the above-mentioned analog switch circuits, wherein an analog signal is inputted to each of the plurality of analog switch circuits, and a switching signal for preventing the analog signals from being simultaneously output from each of the analog switch circuits. And a multiplexer configured to combine the outputs of the analog switch circuits by combining means.

Further, the present invention provides a distribution means for distributing one input analog signal to a plurality of input signals, and inputs each of the distribution analog signals distributed by the means, and performs a switching operation by a given switching signal. , And the analog switch circuit provided for each of the distributed analog signals.

[0010]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration example of an analog switch circuit according to the present invention. In this circuit, switch 1
The configuration and operation of the inverters 2 and 13 and the inverting combiner 14 are the same as those of the related art.
This is a well-known circuit composed of diodes.

In FIG. 1, an analog input signal j is switched by a switch 12 in response to an external switch switching signal q. The switch 13 has an analog signal 0
The level is input, and the switching operation is performed by the switch switching signal q. However, since the input signal is 0, the original output signal also remains 0. Along with these switching operations, not only the switched signal k but also a switch switching leakage signal s is generated at the output of the switch 12, and only the switch switching leakage signal s' is generated at the output of the switch 13. Since these switch switching leakage signals s and s' are both based on the switch switching signal q, the correlation is very strong. Therefore, by inverting and synthesizing these in the inverting synthesizer 14, the switch switching leakage signal s can be substantially canceled. On the other hand, the analog output signal n has the same phase or the inverted phase by passing through the inversion combiner 14, so that there is no problem in the subsequent signal processing.

When the configuration of FIG. 1 is compared with the conventional circuit of FIG. 5, the conventionally used inverting distributor becomes unnecessary, and the circuit configuration can be simplified accordingly.
Therefore, if the circuit shown in FIG. 1 is used as an analog switch circuit of the multiplexer shown in FIG. 3 or the demultiplexer shown in FIG. 4, these multiplexers and demultiplexers can be economically and compactly formed, and particularly, input and output signals are output. The effect increases as the number of analog signals increases. In addition, there is an advantage that the loss of the analog signal level is reduced due to the absence of the inverting distributor.

[0013]

As described above, according to the present invention, the conventional inversion distributor is not required, so that the size and cost can be reduced, and the loss of the analog signal can be reduced. There is an effect that a circuit with a small decrease in N can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an analog switch circuit according to the present invention.

FIG. 2 is a diagram illustrating switching timing of a multiplexer or a demultiplexer.

FIG. 3 is a diagram illustrating a circuit example of a multiplexer.

FIG. 4 is a diagram illustrating a circuit example of a demultiplexer.

FIG. 5 is a block diagram showing a configuration of a conventional analog switch circuit.

[Explanation of symbols]

 12, 13 switch 14 inverting synthesizer

Claims (3)

[Claims] 1. An analog signal is input to an input terminal thereof.
When the external switching signal indicates ON, the input analog signal is passed and output, and when the switching signal indicates OFF, the operation is performed so as not to output the input analog signal. A first switch and an input terminal of the input terminal receive a value of the 0 level of the analog signal as an input signal. When the switching signal indicates ON, the input signal is output as it is, and the switching signal is turned OFF. A second switch that operates so as not to output the input signal when instructing, and a combining unit that combines one of the output of the first switch and the output of the second switch after inverting one of the outputs. An analog switch circuit comprising: 2. A plurality of analog switch circuits according to claim 1, wherein an analog signal is input to each of said plurality of analog switch circuits, and a switching signal is output from each of said analog switches so that said analog signals are not simultaneously output from said analog switch circuits. A multiplexer, which is provided to the circuits and is configured to combine the outputs of the analog switch circuits by combining means. 3. A distribution means for distributing one input analog signal into a plurality of signals, and a distribution operation wherein each of the distribution analog signals distributed by the means is input and a switching operation is performed by a given switching signal. A demultiplexer comprising: the analog switch circuit according to claim 1 provided for each analog signal.