JP2006068090A - Ultrasonograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonograph equipped with a tranceiver circuit with a built-in probe adapted to positive and negative bipolar transmitting signals and the reception. <P>SOLUTION: The ultrasonic probe 15 driving an ultrasonic oscillator 17 by transmitting signals changing into the positive and negative polarity has a small signal amplitude limiting means 16 which applies the transmitting signals to the ultrasonic oscillator 17 when the transmitting signals are at least first prescribed amplitude, a large signal amplitude limiting means 18 outputting the receiver signals, which are received by the ultrasonic oscillator 17 and are equal to or less than second prescribed amplitude much smaller than the transmitting signals, as voltage signals, and a current output type amplifying means 19 which converts the output voltage signals to current signals and is connected to an input terminal of the limiting means 16, having high withstand voltage characteristics. A main body 10 is equipped with a transmitting means 11 outputting the transmitting signals and a voltage converting means 13 which is connected to an output terminal of the transmitting means 11 and converts the current signals output by the amplifying means 19 to voltage signals. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic diagnostic apparatus in which transmission and reception of a signal by an ultrasonic transducer are performed by sharing the same cable, and a probe provided with the ultrasonic transducer has a built-in transmission / reception discriminating means.

  In recent years, an electronic scan type ultrasonic diagnostic system that has multiple channels of ultrasonic transducers and transmits and receives ultrasonic signals using the same cable, has been used to draw images using many subdivided ultrasonic transducers. Is progressing. Since the impedance of this subdivided ultrasonic transducer is generally high, the received signal obtained from the ultrasonic transducer is attenuated by the impedance of the cable connected to the ultrasonic transducer, and sufficient reception sensitivity is obtained. It may not be obtained. In order to solve this problem, a method of reducing a loss due to a cable or the like by inserting a receiving amplifier in an ultrasonic probe has been considered (see, for example, Patent Document 1 or Patent Document 2). These techniques are applied to a unipolar transmission waveform signal whose voltage changes to either positive or negative, but cannot be applied to a bipolar transmission signal.

  When displaying an ultrasonic tomographic image with an ultrasonic diagnostic apparatus, if the signal bandwidth of the ultrasonic waves to be transmitted and received is set wide, it is common that the distance resolution is good, but on the other hand, there is a characteristic that the sensitivity decreases. Known. For this reason, it is necessary to select the characteristics of the transmission waveform according to the purpose depending on the display mode and the diagnostic part. FIG. 4A shows a representative example of a transmission waveform used in the ultrasonic diagnostic apparatus. The waveform A1 in FIG. 6 is a rectangular waveform of the positive one wave 41, the waveform A2 is a rectangular waveform of the bipolar one wave 42, and the waveform A3 is a rectangular waveform of the positive two waves 43.

FIG. 4B shows the frequency analysis results of the three types of rectangular waveforms shown in FIG. 4A. The horizontal axis represents frequency and the vertical axis represents power decibel values. Further, the width Tw of the rectangular waveform is a time width corresponding to ½ of the period of the ultrasonic center frequency F0 to be transmitted, and FIG. 4B shows an example of the frequency analysis result for the waveform of F0 = 2 MHz. . As shown in the figure, in general, the frequency bandwidths of the three types of transmission rectangular waveforms described above are as follows: band characteristic 45 of positive one wave 41> band characteristic 46 of bipolar one wave 42> two positive waves 43 band characteristics 47. Further, the positive one wave 41 and the positive two wave 43 have a frequency of 0 MHz, that is, the spectral power of the direct current component is large, and the bipolar single wave 42 has no direct current component. Therefore, it can be said that the drive with the rectangular waveform of one bipolar polarity shown as the waveform A2 in the figure in which the spectrum power of the signal component is large in the transmission waveform is a drive waveform with high efficiency and good band characteristics.
JP-A-9-33638 JP-A-11-169366

  The conventional transmitter / receiver circuit with a built-in probe described above can be applied to an ultrasonic diagnostic apparatus equipped with a transmitter having a single-wave or two-wave unipolar transmission waveform. When these circuits are applied to an ultrasonic diagnostic apparatus, there is a problem that they are damaged.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic diagnostic apparatus including a transmission / reception circuit with a built-in probe that can be applied to a signal having a positive / negative bipolar transmission waveform and its reception.

  In order to achieve the above object, an ultrasonic diagnostic apparatus of the present invention includes a probe unit that drives an ultrasonic transducer and receives a reception signal from the ultrasonic transducer, and a cable connected to the probe unit via a cable. And a main body unit that generates a transmission signal that changes in both positive and negative polarities applied to the ultrasonic transducer and processes the signal received by the ultrasonic transducer, and the probe unit includes the transmission signal Small amplitude limiting means for applying the transmission signal to the ultrasonic transducer when is equal to or greater than a first predetermined amplitude, and reception by the ultrasonic transducer that is less than a second predetermined amplitude that is extremely smaller than the transmission signal. A large amplitude limiting means for outputting a signal as an output voltage signal, and an output voltage signal output by the large amplitude limiting means is converted into a current signal and connected to the input terminal of the small amplitude limiting means with high withstand voltage characteristics. Current A power type amplifying means, and the main body is connected to an output terminal of the transmitting means for outputting the transmission signal, and the current signal output from the current output type amplifying means is used as a voltage signal. Voltage conversion means for conversion.

  The ultrasonic diagnostic apparatus of the present invention includes a probe unit that drives an ultrasonic transducer and receives a received signal from the ultrasonic transducer, and is connected to the probe unit via a cable, Generating a transmission signal that changes in both positive and negative polarities applied to the child, and processing the signal received by the ultrasonic transducer, wherein the probe unit has the transmission signal equal to or greater than a first predetermined amplitude. At this time, a first switch means for applying the transmission signal to the ultrasonic transducer and a reception signal received by the ultrasonic transducer and having a second predetermined amplitude or less that is extremely smaller than the transmission signal are used as an output voltage signal. A second switch means for outputting, and a current connected to the input terminal of the first switch means with a high withstand voltage characteristic by converting the output voltage signal output by the second switch means into a current signal. Output type Width means, and the main body is connected to an output terminal of the transmission means for outputting the transmission signal, and converts the current signal output from the current output type amplification means into a voltage signal. And a voltage conversion means.

  Furthermore, in the above-described ultrasonic diagnostic apparatus of the present invention, the probe unit includes a plurality of ultrasonic transducers, and each of the ultrasonic transducers includes the small amplitude limiting unit, the large amplitude limiting unit, and the current output type amplification. Means are provided in the probe part, the cable is provided with a plurality of conductors, and the main body part is provided with the voltage conversion means for each conductor.

  Furthermore, in the ultrasonic diagnostic apparatus of the present invention, the small amplitude limiting means is configured by a first diode limiter circuit in which a cathode and an anode are connected in parallel with each other, and a forward voltage drop of the diode is the first voltage drop circuit. A signal having a predetermined amplitude of 1 and an amplitude larger than the forward drop voltage is passed.

  Furthermore, in the ultrasonic diagnostic apparatus according to the present invention, the large amplitude limiting means is forwardly driven by a first bias resistor connected to the first bias power source and a second bias resistor connected to the second bias power source. The cathode-anode connection point of the diode bridge circuit through which a current flows is input, and the other cathode-anode connection point is grounded by a second diode limiter circuit in which the cathode and the anode are connected in parallel differently, The diode bridge is reverse-biased for an excessive input signal to prevent the input signal from passing therethrough, while the small-amplitude input signal having the second predetermined amplitude or less is forward-biased and passed through the diode bridge. It outputs to the other cathode-anode connection point.

  Furthermore, in the ultrasonic diagnostic apparatus according to the present invention, the current output type amplifying means inputs the base of the first transistor that connects the emitter to the third power source via the emitter resistor, and the collector of this transistor is Connected to the source of a second N-channel field effect transistor whose gate is connected to the fourth power supply, the cathode of the diode is connected to the drain thereof, and the anode is connected to the end of the cable on the probe side The voltage signal applied to the base is converted into a current signal flowing through the diode and output.

  Furthermore, in the above-described ultrasonic diagnostic apparatus of the present invention, the current output type amplifying means receives as input the gate of a third N-channel field effect transistor connected to the fifth power source via a source resistor. The cathode of the diode is connected to the drain and the anode is connected to the end of the cable on the probe part side, and the voltage signal applied to the gate is converted into a current signal flowing through the diode and output. It is characterized by.

  The ultrasonic diagnostic apparatus according to the present invention has a transmission / reception discriminating means that can withstand a bipolar transmission signal with low power consumption inside the probe, can transmit and receive with the same cable, and includes a DC component in the transmission / reception signal. Image processing with no broadband characteristics is possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a functional block diagram showing a configuration of a main part related to the present invention in an ultrasonic diagnostic apparatus according to an embodiment of the present invention. FIG. 1 shows a configuration of one channel corresponding to an ultrasonic transducer that transmits and receives an ultrasonic signal in the present embodiment, a transmission control unit that generates a transmission drive signal, and a received signal that is processed to display an image. The image signal processing / display means is omitted.

  As shown in FIG. 1, the present embodiment mainly includes a main body portion 10, a probe portion 15, and a cable 14 that electrically connects them. Further, the main body unit 10 includes a transmission drive unit 11, a preamplifier unit 12, and a voltage conversion element 13. The probe unit 15 includes a small signal amplitude limiting circuit 16, an ultrasonic transducer 17, a large signal amplitude limiter. A circuit 18 and a current output type amplifier circuit 19 are incorporated. In the case of a multi-channel type probe such as an electronic scanning method, these are provided for the number of channels.

  Next, the operation and operation of the present embodiment will be described along the flow of each of the transmission signal and the reception signal.

  As for the transmission signal, the transmission drive unit 11 outputs a signal having a bipolar transmission waveform in accordance with a transmission timing signal input from a transmission control unit (not shown) of the main body unit 10. This bipolar transmission waveform has a large amplitude of typically about 100 Vpp for driving the ultrasonic transducer 17 and is input to the small signal amplitude limiting circuit 16 via the cable 14.

  The impedance between the input and output of the small signal amplitude limiting circuit 16 is several hundreds Ωpp or less at several hundred mVpp or more and smaller than several hundred mVpp for any amplitude of the positive voltage or negative voltage of the input signal. The characteristic is several tens of kΩ or more. Therefore, the input bipolar transmission waveform having a large amplitude passes through the small signal amplitude limiting circuit 16 having a low impedance as it is, and is applied to the ultrasonic transducer 17 connected to the output of the small signal amplitude limiting circuit 16. Excited. By this excitation, an ultrasonic signal is radiated from the ultrasonic transducer 17.

  On the other hand, on the output side of the current output type amplifier circuit 19 connected to the cable 14 in common with the input terminal of the small signal amplitude limiting circuit 16, the bipolar transmission signal applied by the input from the above transmission control means The output type amplifier circuit 19 is configured to increase its output impedance by a high withstand voltage element that can withstand the transmission signal amplitude value, and the current flowing through the current output type amplifier circuit 19 is blocked.

  Furthermore, the bipolar transmission waveform applied to the ultrasonic transducer 17 is also applied to the large signal amplitude limiting circuit 18, which has the input connected to the output of the small signal amplitude limiting circuit 16 together with the ultrasonic transducer 17. However, the bipolar large signal amplitude limiting circuit 18 is switched to an input impedance by a bias resistance of several kΩ to several tens kΩ of the input circuit when the input signal amplitude is several hundred mVpp or more, and is equivalent when the input signal amplitude is smaller than several hundred mVpp. A switch circuit connected to the subsequent circuit of the parallel diode limiter serving as a current source is configured to prevent and protect the bipolar transmission waveform having an excessive amplitude from being input to the current output type amplifier circuit 19.

  Next, the ultrasonic signal radiated from the ultrasonic transducer 17 becomes a reflected signal by the living body tissue of the subject and is received by the ultrasonic transducer 17 again, and the flow of the received signal converted into an electric signal. Will be described.

  Since the signal level of this received signal is usually very small, such as several tens of mVpp, the input / output impedance of the small signal amplitude limiting circuit 16 is high impedance as described above, and no received signal current flows through it. On the other hand, for the small amplitude received signal, the bipolar large signal amplitude limiter circuit 18 has its input circuit turned on, the latter circuit operates as a parallel diode limiter, and the current output connected thereto. A received signal is input to the mold amplifier circuit 19.

  The input reception signal is amplified as a current signal by the current output type amplification circuit 19 and flows through the cable 14 connected to the main body 10, and then flows through the voltage conversion element 13 of the main body 10. The received signal is output as a voltage change at both ends by the impedance of 13.

  The output received signal is amplified by the preamplifier 12 and an ultrasonic image is displayed by an image signal processing / display unit (not shown) of the main body 10.

  According to this embodiment, in the ultrasonic diagnostic apparatus, the driving of the ultrasonic transducer by the bipolar single-wave rectangular waveform that changes to positive and negative polarities with good band characteristics processes the transmission / reception signal built in the probe. It can be performed without damaging the circuit means, and the reflected ultrasonic signal received by this ultrasonic transducer becomes a current signal that is less susceptible to noise by current output type conversion, and flows through the voltage conversion element of the main body, Since it can be returned to the received signal voltage and input to the amplification and image processing means, an ultrasonic image with high image quality performance can be obtained.

  FIG. 2 is a circuit configuration diagram showing a second embodiment of the present invention that further embodies the above-described large embodiment.

  In the present embodiment, as shown in FIG. 2, the ultrasonic diagnostic device main body 20 and the ultrasonic probe unit 25, and the cable 24 for electrically connecting the ultrasonic diagnostic device main body 20 and the ultrasonic probe unit 25. It is composed of Each of the transmission control means for generating the transmission drive signal provided for the transmission of the ultrasonic diagnostic apparatus and the image signal processing / display means for processing the reception signal and displaying the image are complicated and are not shown.

  A transmission drive signal output from a transmission control means (not shown) is input to the ultrasonic device body 20 to form and output a rectangular waveform of the bipolar single wave 42 shown in FIG. A voltage conversion element 23 including a circuit 21, a preamplifier 22, and a resistor R231 is provided. The ultrasonic probe unit 25 is turned on by a small signal amplitude limiting circuit 26 using parallel diodes D261 and D262 having different polarities, an ultrasonic transducer 27, and bias resistors R281 and R282 connected to bias power sources v1 and v2. The diode bridge DH281, DH282, DH283, DH284 and the large signal amplitude limiter circuit 28 of the parallel diodes D281, D282 grounded in different polarities and the collector of the NPN transistor Q291 are connected to the source, and the cathode of the diode D291 is connected to the drain A current output type amplifier circuit 29 by an N channel MOS field effect transistor Q292 of the source follower to be connected is incorporated corresponding to each of the ultrasonic transducers provided.

  Next, the operation and operation of this embodiment will be described along the flow of each signal.

  First, in transmission, a drive signal of a bipolar single-wave rectangular waveform having a positive voltage and a negative voltage with an amplitude of, for example, about 100 Vpp is transmitted and driven by a transmission drive signal output from a transmission control unit (not shown) at a predetermined timing. Output from the circuit 21. The drive signal having the bipolar one-wave rectangular waveform is input to the small signal amplitude limiting circuit 26 via the cable 24 connected to the transmission drive circuit 21. The positive polarity signal of the inputted drive signal is applied as a bipolar drive signal to the ultrasonic transducer 27 through the diode D261 of the parallel diodes D261 and D262 having different polarities, and the negative polarity signal passes through the diode D262. Excite this. The amplitude of the bipolar drive signal at this time is a value obtained by reducing the forward voltage drop of the diodes D261 and D262.

  On the other hand, the bipolar drive signal applied to the ultrasonic transducer 27 is also applied to the input terminal of the large signal amplitude limiting circuit 28. However, the potential on the anode side of the diode DH281 of the diode bridges DH281, DH282, DH283, and DH284, in which the forward voltage drops by the bias resistors R281 and R282, is the voltage drop of the bias resistor R281 in which the forward current flows and the diode DH282. Therefore, the diode DH281 is in a reverse bias voltage state in this positive polarity drive signal, and the diode DH283 is in a forward bias voltage state, so that a current due to the positive polarity drive signal also flows, The potential on the cathode side becomes high, and the diode DH284 is reverse biased and blocked. Further, the negative polarity driving signal is in a reverse bias voltage state because the potential on the cathode side of the diode DH283 is determined by the forward voltage drop of the diode DH4 and the diode D282 and the voltage drop of the bias resistor R282 through which the forward current flows. Since DH281 is in the forward bias voltage state, it passes, but the diode DH28 is in the reverse bias state and is also blocked. That is, a bipolar drive signal having a large amplitude of about 100 Vpp is blocked by the biased diode bridge and does not reach the output.

  A drive signal having a bipolar single-wave rectangular waveform is also applied to the diode D291 at the output end of the current output type amplifier circuit 29 connected to the cable 24. Since these bipolar drive signals are applied to the anode of the diode D291, the negative polarity signal is in the reverse direction of the diode and is blocked. Further, since the positive signal passes through the diode D291 and is added to the drain terminal of the N channel MOS field effect transistor Q292 of the source follower, the drain terminal has a high impedance with respect to the positive signal, and the N channel MOS An element having a higher withstand voltage between the drain and source of the field effect transistor Q292 than the maximum value of the transmission voltage is used to prevent the element from being damaged and to prevent it.

  Next, in reception, an ultrasonic wave is transmitted from the ultrasonic transducer 27, and an ultrasonic reflection signal reflected by the biological tissue of the subject is received by the ultrasonic transducer 27 again. The ultrasonic transducer 27 converts this into an electrical signal as a received signal, and outputs it with a very small signal level, usually several tens mVpp or less.

  The reception signal output from the ultrasonic transducer 27 has a small forward voltage drop value of the parallel diodes D261 and D262 of the small signal amplitude limiting circuit 26, for example, a forward voltage drop value of a normal silicon diode is as small as about 0.7V. Therefore, no current flows through these diodes.

  On the other hand, this received signal is a diode bridge DH281, DH282, DH283, DH284 in which a steady current flows in the forward direction via the bias resistors R281, R282 between the voltage source v1 and the power source v2 of the large signal amplitude limiting circuit 28. Is input. In the input received signal, since the diode bridge is in an ON state with a low impedance, a signal having the same signal level appears at the base terminal of the NPN transistor Q291 of the current output type amplifier circuit 29.

  The NPN transistor Q291, whose received signal is input to the base terminal and whose emitter terminal is connected to the power source v3 via the emitter resistor R291, has a steady current required for the received signal current determined by this emitter voltage and the power source v3. Since this current amplification factor is sufficiently large, the signal current flowing through the collector of the NPN transistor Q291 is approximately determined by the signal voltage generated at the emitter and the resistance value of the emitter resistor R291.

  The gate terminal of the N channel MOS field effect transistor Q292 connected in the source follower of the current output type amplifier circuit 29 is connected to the power source v4, and the signal current flowing through the collector of the NPN transistor Q291 is from the source side of the N channel MOS field effect transistor Q292. Flows to the drain. Therefore, it flows through the diode D291 connected to the drain, and the received signal current is converted into the received signal voltage by the resistor R231 of the voltage converting element 23 of the main body 20 connected by the cable 24. The received signal voltage is amplified by the preamplifier 27 of the main body unit 20, and the received signal is processed by an image signal processing / display unit of the ultrasonic diagnostic apparatus body unit 20 (not shown) to display an ultrasonic image.

  When the ultrasonic diagnostic apparatus is an electronic scan type and includes a plurality of ultrasonic transducers in the probe, each of the ultrasonic transducers includes the voltage conversion element 23, the small signal amplitude limiting circuit 26, and the large signal amplitude. A limiting circuit 28 and a current output type amplifier circuit 29 are provided.

  According to the present embodiment, a circuit that allows only a large-amplitude drive signal using the forward characteristics of a parallel diode to pass through the probe, and a circuit that limits a bipolar large-amplitude signal by a diode bridge to which a bias voltage is added in the previous stage. And a current output type amplification conversion circuit capable of withstanding the drive transmission voltage in the subsequent stage, and an impedance element for converting the reception current into voltage is provided in the output to the main body, so that the transmission signal of the bipolar waveform with good band characteristics and Since the received signal can be processed, an ultrasonic image with high image quality performance can be obtained. In addition, since the impedance element for converting the received current into voltage is provided on the main body side, there is an effect that the power consumption can be reduced while suppressing the heat generation inside the probe.

  FIG. 3 is a circuit configuration diagram showing a more specific third embodiment.

  As shown in FIG. 3, the present embodiment mainly includes an ultrasonic diagnostic apparatus main body 30, an ultrasonic probe section 31, and a cable 34 for electrically connecting the main body section 30 and the probe section 31. Is done. In the detailed circuit configuration that constitutes each of these parts, parts that are the same configuration or elements as the detailed circuit configuration of the second embodiment shown in FIG. 2 are denoted by the same reference numerals as in FIG. . In the third embodiment shown in FIG. 3, a circuit portion different from the second embodiment is a current output side amplifying circuit 32 using an N-channel MOS field effect transistor provided in the probe 31.

  In the current output type amplifier circuit 32 of this embodiment, an N-channel MOS field effect transistor QH321 having a gate terminal connected to the output of the large signal amplitude limiting circuit 28, a cathode connected to the drain terminal thereof, and an anode connected to the cable 34 And a diode DH321 connected to the probe side end. The source / drain withstand voltage of the diode DH321 and the N-channel MOS field effect transistor QH321 is an element having a withstand voltage characteristic that can withstand a transmission drive voltage transmitted via the cable 34, and the resistor R321 is a source resistance.

  In the ultrasonic diagnostic apparatus main body 30 or the probe unit 31 of the present embodiment shown in FIG. 3, the circuits denoted by the same reference numerals as those in FIG. 2 operate and operate in the same manner as described in the second embodiment. The operation and operation of the present embodiment will be specifically described for the high withstand voltage current output type amplifier circuit 32 having the circuit configuration different from that of the second embodiment.

  The bipolar one-wave rectangular wave ultrasonic transmission drive signal input from the main body unit 30 to the probe unit 31 via the cable 34 is input to the small signal amplitude limiting circuit 26 and applied to the anode of the diode DH321. The

  The applied negative signal is blocked because the diode DH321 is in a reverse bias state. The positive signal flows through the diode DH321 and is applied to the drain terminal of the N-channel MOS field effect transistor QH321. However, since the N-channel type is used, the drain terminal is higher than the positive signal. It is also blocked by using an element having a drain-source withstand voltage characteristic that becomes an impedance and is higher than the maximum value of the ultrasonic transmission drive voltage.

  On the other hand, the received signal input from the large signal amplitude limiter circuit 28 to the current output type amplifier circuit 32 has an N-channel MOS type electric field in which the source terminal is connected to the power source v6 via the source resistor R321 and a steady current flows. Applied to the gate terminal of the effect transistor QH321. Since this applied received signal appears at its source terminal, a current change determined by the received signal voltage and the source resistance R321 is output to the drain terminal and becomes a received signal current. This received signal current flows through the resistor R231 of the voltage conversion element 23 of the main body 30 via the cable 34, and the received signal is amplified by the preamplifier 27 to obtain an image of the main body 30 (not shown). The received signal is processed by the signal processing / display means to display an ultrasonic image.

  According to the present embodiment, the current output type amplifier circuit can be constituted by an N-channel MOS field effect transistor and a diode, and the additional power source can be simplified as one on the source side. Wiring can be reduced and costs can be reduced. In addition to the reduction in the number of parts, the power consumption is further suppressed, so that no countermeasures against heat generation are required, and the probe can be made smaller.

The block block diagram which shows the 1st Embodiment of this invention. The circuit block diagram which shows the 2nd Embodiment of this invention. The circuit block diagram which shows the 3rd Embodiment of this invention. The figure which shows a different ultrasonic drive waveform and its frequency characteristic.

Explanation of symbols

10, 20, 30 ... main body,
11, 21 ... transmission drive unit,
12, 22 ... Preamplifier,
13, 23 ... voltage conversion element,
14, 24, 34 ... cable,
15, 25, 31 ... probe part,
16, 26... Small signal amplitude limiting circuit,
17, 27 ... ultrasonic transducer,
18, 28... Large signal amplitude limiting circuit,
19, 29, 32 ... current output type amplifier circuit,
41 ... Positive wave waveform
42: Bipolar single wave waveform,
43 ... Positive two-wave waveform,
45... Frequency characteristics of a positive single wave waveform,
46: Frequency characteristics of a single waveform of bipolar polarity,
47: Frequency characteristics of a positive two-wave waveform.

Claims (7)

A probe unit that drives an ultrasonic transducer and receives a received signal from the ultrasonic transducer, and a transmission that is connected to the probe unit via a cable and changes to positive and negative polarities applied to the ultrasonic transducer A main body for generating a signal and processing the signal received by the ultrasonic transducer,
The probe section is
A small amplitude limiting means for applying the transmission signal to the ultrasonic transducer when the transmission signal has a first predetermined amplitude or more;
Large amplitude limiting means for receiving a reception signal having a second predetermined amplitude or less, which is received by the ultrasonic transducer and extremely smaller than the transmission signal, as an output voltage signal;
The output voltage signal output by the large amplitude limiting means is converted into a current signal, and has a current output type amplifying means connected to the input terminal of the small amplitude limiting means with high withstand voltage characteristics,
The main body is
A transmission means for outputting the transmission signal;
Voltage conversion means connected to the output end of the transmission means, for converting the current signal output from the current output type amplification means into a voltage signal;
An ultrasonic diagnostic apparatus comprising: A probe unit that drives an ultrasonic transducer and receives a received signal from the ultrasonic transducer, and a transmission that is connected to the probe unit via a cable and changes to positive and negative polarities applied to the ultrasonic transducer A main body for generating a signal and processing the signal received by the ultrasonic transducer,
The probe section is
First switch means for applying the transmission signal to the ultrasonic transducer when the transmission signal has a first predetermined amplitude or more;
Second switch means for receiving, as an output voltage signal, a reception signal received by the ultrasonic transducer and having a second predetermined amplitude or less that is extremely smaller than the transmission signal;
An output voltage signal output by the second switch means is converted into a current signal, and has a current output type amplifying means connected to the input end of the first switch means with a high withstand voltage characteristic;
The main body is
A transmission means for outputting the transmission signal;
Voltage conversion means connected to the output end of the transmission means, for converting the current signal output from the current output type amplification means into a voltage signal;
An ultrasonic diagnostic apparatus comprising:   The probe unit includes a plurality of ultrasonic transducers, and each of the ultrasonic transducers is provided with the small amplitude limiting unit, the large amplitude limiting unit, and the current output type amplifying unit in the probe unit, and the cable includes a plurality of cables. The ultrasonic diagnostic apparatus according to claim 1, wherein the main body portion includes the voltage conversion unit for each of the conductive wires.   The small amplitude limiting means is constituted by a first diode limiter circuit in which a cathode and an anode are connected in parallel with each other, and a forward drop voltage of the diode is the first predetermined amplitude. 4. The ultrasonic diagnostic apparatus according to claim 1, wherein a signal having a large amplitude is passed.   The large amplitude limiting means includes a cathode-anode connection point of a diode bridge circuit in which a forward current flows by a first bias resistor connected to a first bias power source and a second bias resistor connected to a second bias power source. And the other cathode-anode connection point is grounded by a second diode limiter circuit in which the cathode and the anode are connected in parallel with each other, and the diode bridge is reverse-biased for an excessive input signal. The input signal is prevented from passing through, while the small-amplitude input signal having the second predetermined amplitude or less is passed through with a forward bias and output to the other cathode-anode connection point. The ultrasonic diagnostic apparatus according to any one of claims 1, 3, and 4.   The current output type amplifying means takes as input a base of a first transistor that connects the emitter to the third power source through an emitter resistor, and the collector of this transistor connects the second N to the gate of the fourth power source. The channel field effect transistor is connected to the source, the cathode of the diode is connected to the drain of the channel field effect transistor, the anode is connected to the end on the probe side of the cable, and the voltage signal applied to the base is 6. The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic diagnostic apparatus converts the current signal to flow through a diode and outputs the current signal.   The current output type amplifying means has a gate of a third N-channel field effect transistor connected to a fifth power source through a source resistor as an input, a cathode of a diode is connected to the drain of the transistor, and an anode thereof is A voltage signal applied to the gate is converted into a current signal flowing through the diode and is output by being connected to an end portion of the cable on the probe portion side. The ultrasonic diagnostic apparatus in any one of.