JPH0787304B2 - Amplification device for recording electrocardiogram signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used for a portable long-term electrocardiographic apparatus for recording an electrocardiogram signal for a long time by an AC bias direct recording method and reproducing the recorded signal in a short time later. The present invention relates to an electrocardiographic signal recording amplifier suitable for

[Outline of Invention]

According to the present invention, in an electrocardiographic signal recording amplifier equipped with a differential amplifier, an amplifier for amplifying the output of the differential amplifier is provided, and a part of the output of the amplifier is fed back by a limiter and a non-inverting integrator. The circuit is fed back as an inverting input of the amplifier to prevent deterioration of the in-phase signal rejection ratio of the differential amplifier and to prevent narrow deterioration of the dynamic range of the amplifier.

Further, a high-pass filter is provided between the differential amplifier and the amplifier, and a feedback amount adjusting amplifier is provided in the feedback circuit so that the baseline fluctuation of the electrocardiogram signal can be suppressed in an extremely short time. is there.

[Conventional technology]

A conventional portable long-time electrocardiogram device is composed of a recorder that records an electrocardiogram signal for a long time by an AC bias direct recording method and a regenerator that reproduces the recorded signal in a short time.

The recorder is provided with an electrocardiographic signal recording amplifier including a differential amplifier for amplifying an electrocardiographic signal obtained from a plurality of electrodes attached to the surface of the body and supplying the amplified electrocardiographic signal to a subsequent recording circuit.

In the conventional portable long-term electrocardiogram device having such a configuration, when recording an electrocardiogram signal in the recorder, movement of the body, contact failure of electrodes attached to the surface of the body, extension of the electrode cord, or temperature change. Due to the influence of the surrounding environment such as DC offset and wandering (wand
The baseline fluctuation due to ering) may occur.

When this baseline fluctuation occurs, the fluctuation component is superimposed on the electrocardiogram signal, which causes waveform saturation of the recorder (loss of the recording signal due to exceeding the saturation level of the differential amplifier). Recording becomes impossible.

Therefore, as a conventional amplifying device that suppresses this baseline fluctuation, there is, for example, one shown in FIGS. 3 and 4.

The device shown in FIG. 3 comprises a differential amplifier group 1 and a feedback circuit provided with a limiter 2 and an inverting integrator 3, and the differential amplifier 1 is necessary for recording an electrocardiogram signal in a subsequent recording circuit. Amplify to a certain size and output.

The output is also input to the limiter 2 in which a predetermined limiter level is set, and when the electrocardiogram signal supplied from the differential amplifier 1 exceeds the predetermined level due to the baseline fluctuation in the electrocardiogram signal, the level is changed. The excess signal component is extracted and output to the inverting integrator 3.

The inverting integrator 3 inverts and integrates the output of the limiter 2 and feeds back the inverted integrated output as a non-inverting input of the differential amplifier 1 to suppress the baseline fluctuation of the electrocardiogram signal.

On the other hand, in the device shown in FIG. 4, an amplifier 5 for amplifying the output of the differential amplifier 1 is added to the device shown in FIG. 3, and the gain necessary for amplifying an electrocardiogram signal is increased by the differential amplifier 1 and this amplifier 5. In addition, the inverting integration output of the inverting integrator 3 is fed back as the non-inverting input of the amplifier 5 to suppress the baseline fluctuation of the electrocardiogram signal.

[Problems to be Solved by the Invention]

However, in the conventional device shown in FIG. 3, since the inverting integration output of the inverting integrator 3 is fed back as the non-inverting input of the differential amplifier 1, the common mode noise included in the electrocardiogram signal is fed into the differential amplifier 1. It cannot be completely removed, and the common mode rejection ratio (CMR
R) was deteriorated.

Further, in the conventional apparatus shown in FIG. 4, since the inverted integrated output is not fed back to the differential amplifier 1, the common-mode signal rejection ratio does not deteriorate as described above, but the amplifier 5 is substantially the same. There was a drawback that the dynamic range was narrowed.

That is, since the inverting integration output of the inverting integrator 3 is transferred as the non-inverting input of the amplifier 5, the input of the amplifier 5 is the addition signal of the fed back inverting integration output and the electrocardiogram signal. Therefore, in order to obtain an amplified output at the same level as when only the electrocardiogram signal is input from the amplifier 5,
It is necessary to double the gain.

However, when the gain of the amplifier 5 is increased in this way, there is a problem that the bandwidth is narrowed and the high frequency band is easily distorted, and the dynamic range of the amplifier 5 is substantially narrowed.

The present invention solves the above problems and can suppress the baseline fluctuation of the electrocardiogram signal without causing deterioration of the common-mode rejection ratio of the differential amplifier and narrow deterioration of the dynamic range of the amplifier. An object is to provide a recording amplifying device.

Another object is to be able to suppress the baseline fluctuation of the electrocardiogram signal in an extremely short time.

[Means for Solving the Problems]

In order to solve the above problems, the present invention relates to an electrocardiographic signal recording amplifying apparatus including a differential amplifier for amplifying an electrocardiographic signal obtained from an electrode, and an amplifier for amplifying an output of the differential amplifier and an output of the amplifier Is provided with a limiter for extracting a signal component exceeding a predetermined level and a non-inverting integrator for integrating the output of the limiter, and the output of the non-inverting integrator is fed back to the amplifier as an inverting input. It is a feedback circuit that is formed.

Further, a high-pass filter is provided between the differential amplifier and the amplifier, and a feedback amount adjusting amplifier for adjusting the feedback amount of the output of the non-inverting integrator to the amplifier is preferably provided in the feedback circuit. .

[Work]

According to the electrocardiographic signal recording apparatus of the present invention, the electrocardiographic signal obtained from the electrodes is amplified by the differential amplifier and the amplifier to a size required for recording in the subsequent recording circuit.

Then, a part of the output of the amplifier is input to the limiter of the feedback circuit, and when the baseline fluctuation occurs in the electrocardiogram signal and the output from the amplifier exceeds a predetermined level, the limiter outputs a signal component that exceeds the predetermined level. Extract and output to non-inverting integrator.

The non-inverting integrator integrates the output of this limiter and feeds it back as the inverting input of the amplifier. By this feedback action, the baseline fluctuation generated in the electrocardiogram signal is canceled and suppressed in the amplifier.

Further, when a high-pass filter is provided between the differential amplifier and the feedback circuit and a feedback amount adjusting amplifier is provided, the baseline fluctuation component, which is mainly a DC or low frequency signal, is passed through the high band. Most of them can be removed by a filter, and the feedback amount adjustment amplifier adjusts the feedback amount of the integrated output of the non-inverting integrator to an appropriate amount to significantly reduce the baseline fluctuation suppression time. It can be shortened.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 (A) and 1 (B) are circuit configuration diagrams of a recorder and a regenerator of a portable long-term electrocardiogram device embodying the present invention.
The same parts as those in FIGS. 3 and 4 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 (A) shows the structure of the recorder, 7 to 9 are electrodes attached to the surface of the body, and the differential amplifier 1 amplifies the electrocardiogram signals obtained from these electrodes 7 to 9 and passes them through the high frequency band. Output to filter 10.

The high-pass filter 10 removes a baseline fluctuation component that is mainly a direct current or a low frequency signal, and passes an electrocardiogram signal having a frequency band of 0.05 to 100 Hz without omission,
The cut-on frequency is set to an appropriate value below 0.05 Hz.

Therefore, the electrocardiographic signal output from the differential amplifier 1 passes through the high-pass filter 10 so that most of the baseline fluctuation component superimposed on the electrocardiographic signal is removed and the electrocardiographic signal is supplied to the amplifier 5. To be done.

The amplifier 5 amplifies the electrocardiogram signal output from the high-pass filter 10 to a size required for recording on the magnetic tape 17 by the recording circuit including the subsequent adder 14, bias oscillator 15 and magnetic head 16, Output to adder 14.

A part of the output signal is a feedback circuit 12 formed by the limiter 2, the non-inverting integrator 11, and the feedback amount adjusting amplifier 13.
Is also entered.

When the electrocardiogram signal supplied from the amplifier 5 exceeds a predetermined level due to the baseline fluctuation component that cannot be removed by the high-pass filter 10, the limiter 2 outputs the signal component exceeding the predetermined level to the electrocardiogram. It is extracted from the signal and output to the non-inverting integrator 11.

The non-inverting integrator 11 integrates the output of the limiter 2 without inverting, and feeds the integrated output back to the inverting input terminal of the amplifier 5 via the feedback amount adjusting amplifier 13.

The feedback amount adjusting amplifier 13 amplifies the integral output of the non-inverting integrator 11 to an appropriate magnitude so that the baseline fluctuation generated in the electrocardiogram signal can be suppressed completely and in a short time. Then, the amplified integrated output is fed back to the inverting input terminal of the amplifier 5 by the feedback circuit 12.

The feedback of the integrated output to the amplifier 5 cancels the baseline fluctuation component superimposed on the electrocardiogram signal, and suppresses the baseline fluctuation generated in the electrocardiogram signal in an extremely short time.

In addition, according to the present invention, the differential amplifier 1, the high-pass filter 10, the amplifier 5 and the feedback circuit 12 formed by the limiter 2, the non-inverting integrator 11 and the feedback amount adjusting amplifier 13 are provided. However, the high-pass filter 10 and the feedback amount adjusting amplifier 13 are not essential.

The adder 14 adds the electrocardiogram signal amplified by the amplifier 5 and the AC bias signal generated by the bias oscillator 15 and supplies it to the magnetic head 16. By this,
The magnetic head 16 records an electrocardiogram signal on the magnetic tape 17.

The adder 14 and the bias oscillator 15 are related to an AC bias direct recording system which is generally used for audio tape recorders.

FIG. 1 (B) shows the structure of a regenerator, in which an electrocardiogram signal recorded on a magnetic tape 17 is detected by a regenerating magnetic head 18, and a preamplifier 19 amplifies the signal to a predetermined amplitude, and an amplitude equalizing circuit is shown.
The reduced differential characteristic and the high frequency loss are compensated by 20 and a predetermined electrocardiographic signal is output to the output terminal 21.

According to this embodiment, when a baseline fluctuation occurs in the electrocardiogram signals obtained from the electrodes 7 to 9, the high-pass filter 10 causes most of the baseline fluctuation components, which are direct-current or low-frequency signals, to be electrocardiograms. Removed from the signal.

Further, the baseline fluctuation component that could not be removed by the high-pass filter 10 is amplified to an appropriate magnitude by the feedback amount adjusting amplifier 13 and fed back as an inverting input of the amplifier 5 via the feedback circuit 12. By the integrated output of the non-inverting integrator 11, which is completely canceled in the amplifier 5, the baseline fluctuation generated in the electrocardiogram signal is suppressed in an extremely short time.

FIG. 2 is a diagram showing a comparison of examples of suppressing the baseline fluctuation between the conventional amplifying devices shown in FIGS. 3 and 4 and the above-described embodiment, in which (a) is shown in FIG. The conventional device shown,
(B) is a conventional apparatus shown in FIG. 4, and (C) is an example of suppressing the baseline fluctuation according to the above-described embodiment.

As is clear from the figure, in the case of the device of the example of (c), compared with the case of the conventional device of (a) and (b),
The fluctuation b occurring on the baseline a of the electrocardiogram signal is suppressed in an extremely short time.

As described above, according to the above-described embodiment, when the base line fluctuation occurs in the electrocardiogram signal, most of the base line fluctuation component which is the direct current or the low frequency signal is removed by the high-pass filter 10 and As for the baseline fluctuation component that could not be removed by the high-pass filter 10, the integrated output of the non-inverting integrator 11 is amplified by the feedback amount adjusting amplifier 13 to an optimum size and fed back to the amplifier 5. As a result, it is removed in the amplifier 5 in a very short time.

Therefore, it is possible to shorten the suppression time of the baseline fluctuation generated in the electrocardiogram signal.

Further, since the feedback signal from the feedback circuit 12 is configured to be fed back to the amplifier 5 instead of the differential amplifier 1, the common mode noise included in the electrocardiogram signal is completely removed in the differential amplifier 1. The phase signal rejection ratio (CMRR) does not deteriorate.

Furthermore, since the feedback circuit 12 is configured to feed back the integrated output of the non-inverting integrator 11 as the inverting input of the amplifier 5, the inverted output is fed back as the non-inverting input of the amplifier 5 like a conventional device. Moreover, it is not necessary to double the gain of the amplifier 5. Therefore, it is possible to prevent the dynamic range from being narrowed by increasing the gain of the amplifier 5.

It should be noted that such an effect can be obtained without the feedback amount adjusting amplifier 13 of the high-pass filter 10.

〔The invention's effect〕

As described above, the amplifying apparatus for recording an electrocardiogram signal according to the present invention does not deteriorate the common-mode signal rejection ratio of the differential amplifier and narrows the dynamic range of the amplifier without changing the baseline of the electrocardiogram signal. Can be suppressed.

Further, when a high-pass filter is provided between the differential amplifier and the feedback circuit and a feedback amount adjusting amplifier is provided, the baseline fluctuation generated in the electrocardiogram signal can be suppressed in an extremely short time. .

[Brief description of drawings]

1 (A) and 1 (B) are block diagrams showing the circuit configurations of a recorder and a regenerator of a portable long-term electrocardiogram device embodying the present invention, and FIG. 2 is a conventional device of FIGS. 3 and 4. And a diagram showing an example of suppressing baseline fluctuation in comparison with the embodiment shown in FIG. 1 (A), and FIGS. 3 and 4 are block diagrams showing different examples of a conventional electrocardiographic signal recording amplifying apparatus. Is. 1 ... Differential amplifier, 2 ... Limiter 5 ... Amplifier, 7-9 ... Electrode 10 ... High-pass filter, 11 ... Non-inverting integrator 12 ... Feedback circuit 13 ... Feedback amount adjusting amplifier

Claims (2)

[Claims] 1. An electrocardiographic signal recording amplifier comprising a differential amplifier for amplifying an electrocardiographic signal obtained from an electrode, wherein an amplifier for amplifying an output of the differential amplifier and a part of an output of the amplifier are inputted. A limiter for extracting a signal component exceeding a predetermined level and a non-inverting integrator for integrating the output of the limiter are provided, and a feedback circuit for feeding back the output of the non-inverting integrator to the amplifier as an inverting input is formed. An amplifying device for recording an electrocardiogram signal, which is characterized in that: 2. The electrocardiographic signal recording amplifier according to claim 1, wherein a high-pass filter is provided between the differential amplifier and the feedback circuit, and a feedback amount of the output of the non-inverting integrator to the amplifier. An amplifier device for recording an electrocardiogram signal, which is provided with an amplifier for adjusting a feedback amount for adjusting.