JP2001087263A - Transmission circuit of ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of heating, and amplify an optional waveform in a transmission circuit of an ultrasonograph. SOLUTION: A pedestal clamp circuit (a bias setting circuit) 30 generates a pair of pedestal clamp pulses (bias pulses) Vb1, Vb2 each having a pulse width corresponding to an original transmission signal and having a bipolar symmetric property. A pseudo-linear amplifier 32 sets a bias point according to a level of the pedestal clamp pulses Vb1, Vb2, and linearly amplifies the original transmission signal only in a period of the pulses to thereby become 0 bias on the outside of the pulse period so as to remove useless electric power consumption as well as to eliminate a problem of heating. The pseudo-linear amplifier is desirably composed of a high speed negative feedback type linear amplifier having a bipolar symmetric property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit of an ultrasonic diagnostic apparatus, and more particularly to setting a bias.

[0002]

2. Description of the Related Art There is known an ultrasonic diagnostic apparatus which displays a tomographic image or a Doppler image by transmitting and receiving ultrasonic waves. In these ultrasonic diagnostic apparatuses, an electronic focusing technique for converging an ultrasonic beam is widely used to obtain high image quality.

However, since the focused ultrasonic beam has some side lobes in the directional characteristics, artifacts are displayed on the screen, which causes deterioration in image quality. As a method for reducing sidelobes that cause artifacts, an apodization technique for weighting transmission waves is applied to an ultrasonic diagnostic apparatus.

A conventional ultrasonic diagnostic apparatus generally has a harmonic image based on a B mode, a continuous wave Doppler mode (CW), a CFM (color flow mapping) mode, and a second harmonic component in an echo. It has a plurality of display modes such as a jing mode.

In such an ultrasonic diagnostic apparatus having a plurality of display modes, a transducer is used in accordance with each display mode in view of the relationship between ultrasonic energy in a living body and a signal-to-noise ratio (SNR). It is necessary to change the waveform of the transmission wave to be added to and the peak value thereof.

For example, in the CW mode, it is required that the transmission wave be a sine wave from the viewpoint of SNR and that the content of harmonics be suppressed low. On the other hand, in the case of harmonic imaging using the second harmonic of the reflected wave in the living body It is necessary to suppress the second harmonic of the transmitted wave sufficiently lower than the second harmonic of the reflected wave in the living body.

Therefore, in such an ultrasonic diagnostic apparatus,
There is a need for a transmission circuit that can drive a vibrator with an arbitrary waveform, such as a pulse wave, a sine wave, and a Gaussian wave.

FIG. 6 shows an example of a transmission circuit for performing transmission apodization in a conventional ultrasonic diagnostic apparatus. The transmission circuit includes a power supply unit 10, a transmission voltage control unit 12, pulsar units C1 to C4, and voltage limiters D1 to D4.
The power supply unit 10 supplies a constant voltage Vdc to the pulsar units C1 to C4.

The pulsar units C1 to C4 output an output voltage Vdc based on drive pulses α1 to α4 corresponding to each channel.
Are output. Transmission voltage control unit 1
2, the transmission voltage control signals φ1 to φ4 are applied to the voltage limiters D1 to D4.
D4, the voltage limiters D1 to D4 clip the voltages of the constant voltage pulses β1 to β4, and the transducers td1 to td4 of the ultrasonic probe 14 with pulses γ1 to γ4 of different peak values.
Drive. The apodization of transmission is executed in the above procedure.

However, when the power supply voltage of the pulsar unit is Vdc
Β1 to β4 are always output at the maximum output voltage, and at the time of the minimum drive pulse due to apodization,
The output voltage of the difference is consumed in the voltage limiters D1 to D4. Therefore, the power loss is large, and the problem of heat generation in the entire circuit increases.

On the other hand, since the transmission wave is a pulse wave, a filter for holding down the second harmonic of the transmission wave sufficiently lower than the second harmonic of the in-vivo reflected wave in the harmonic imaging mode is separately provided. It is necessary to provide for each channel or separately provide a dedicated transmission circuit.

Further, since the pulsar units C1 to C4 and the voltage limiters D1 to D4 are constituted by nonlinear circuits, it is needless to say that the vibrator cannot be driven by a sine wave, a Gaussian wave or any other arbitrary waveform.

Therefore, in order to provide a high-performance, multifunctional ultrasonic diagnostic apparatus, it is necessary to provide a dedicated transmission circuit for each of various transmission waves, which causes heat generation and cost problems.

FIG. 7 shows another example of a transmission circuit for performing apodization in a conventional ultrasonic diagnostic apparatus. This transmission circuit includes a clamp unit 20, a voltage comparison unit 22, a voltage-current conversion unit 24, a high-voltage current control unit 26, and a transformer 28 with a tap.
It is provided corresponding to TD. A constant high voltage HV (for example, 100 V) is connected to each tap of the transformer 28, and each circuit is off when there is no signal.

The clamp section 20 fixes the transmission pulse Pulse 1 and the transmission control signal Vpc cont.1 to predetermined values based on the power supply -Vee, and supplies them to the voltage comparison section 22. The voltage comparison unit 22 includes a transmission pulse Pu having a fixed potential.
lse 1 is clipped at the potential Vpc1 based on the transmission control signal Vpc cont.1, and a voltage pulse having a peak value α1 is supplied to the voltage-current converter 24. The voltage-current converter 24 generates a current pulse β1 based on the current value flowing into R1 by the voltage pulse having the peak value α1 generated by the voltage comparator 22, and generates a high-voltage current controller 26 composed of an FET switch.
To supply. The high-voltage current controller 26 constituted by an FET switch is turned on by a voltage generated by a current flowing through R2 and R3 with the power supply Vcc as a reference voltage by the current pulse β1, and supplies the current pulse β1 to the transformer 28, The transformer 28 converts the current pulse β1 into a high-voltage pulse and drives a vibrator TD (not shown). The apodization of transmission is executed in the above procedure.

The transmission circuit stops its operation when there is no signal, because the FET switch constituting the high voltage current control unit 26 is off. Accordingly, power consumption when there is no signal is zero (0), which is advantageous in terms of heat generation.

However, since the transmission wave is a pulse wave,
In the harmonic imaging mode, a filter for holding down the second harmonic of the transmission wave sufficiently lower than the second harmonic of the in-vivo reflected wave is separately provided for each channel, or separately provided for exclusive use. It is necessary to provide a circuit. Also, since a transformer is used, it is difficult to reduce the size of the circuit, reduce the cost, and integrate the circuit into an integrated circuit.

In this transmission circuit, since the clamp unit 20 and the voltage comparison unit 22 are constituted by non-linear circuits,
It goes without saying that the vibrator cannot be driven with a sine wave, a Gaussian wave or any other arbitrary waveform.

[0019]

As described above, in the above-described conventional transmission circuit, since the circuit is constituted by a non-linear circuit system, the transmission wave becomes a pulse wave.
In the monic imaging mode, it is necessary to separately provide a filter for each channel to suppress the second harmonic of the transmission wave sufficiently lower than the second harmonic of the reflected wave in the living body.

In addition, since low-voltage output transmission is performed at the time of Doppler (CW), a dedicated low-voltage linear amplifier for transmitting a sine wave, that is, a so-called linear circuit type transmission circuit is separately provided from the viewpoint of SNR.

Therefore, it was not possible to drive the vibrator with an arbitrary waveform from a low voltage to a high voltage, for example, a pulse wave, a sine wave, a Gaussian wave, or the like, with one transmission circuit.

It should be noted that JP-A-5-344970, JP-A-8-252251, and JP-A-10-57373.
JP, JP-A-11-56839, U.S. Pat.
No. 821706 discloses a related technique.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a transmission circuit of an ultrasonic diagnostic apparatus capable of performing linear amplification and reducing heat generation.

[0024]

(1) In order to achieve the above object, the present invention provides a bias setting for outputting a pair of biasing pulses having bipolar symmetry having a pulse width corresponding to an original transmission signal. And a drive circuit whose operating period and operating point are determined by the pair of bias pulses and amplifies the original transmission signal.

According to the above configuration, the bias setting circuit generates a pair of bias pulses, and the drive circuit amplifies the original transmission signal according to the pair of bias pulses. That is, the operation period of the drive circuit is defined by the pulse width of the pair of bias pulses, and the operating point of the drive circuit is defined by the level of each of the pair of bias pulses. Therefore, a bias is formed only during a period in which the operation is necessary, that is, an operable state is set, so that the problem of heat generation can be dealt with. If the drive circuit is operated linearly by appropriately setting the level of the bias pulse, amplification can be performed under desired operating conditions.

Preferably, the drive circuit has a circuit for supplying a bias current for a period corresponding to a pulse width of the pair of bias pulses. That is, in other periods, the supply of the bias current is stopped, whereby the operation of the circuit is effectively stopped, and unnecessary power consumption is suppressed.

Preferably, the pair of bias pulses rise before the start point of the original transmission signal by a standby time. According to this configuration, the circuit can be stabilized prior to the amplification of the original transmission signal.

Preferably, the drive circuit has a circuit for fixedly setting an operating point in a linear amplification region in accordance with the level of the pair of bias pulses. According to this configuration, linear amplification of an arbitrary waveform can be achieved by operating the drive circuit linearly.

Preferably, the drive circuit has a complementary symmetrical circuit configuration in which all stages from input to output are DC-coupled. According to this configuration, responsiveness can be improved. Since it is a complementary type, amplification is performed independently for each polarity component, and finally components of both polarities are integrated.

Preferably, the drive circuit is a high-speed negative feedback amplifier. According to this configuration, the operating point is stabilized, and a higher frequency, a higher speed response, a lower distortion rate of the waveform, and the like are achieved.

Preferably, the bias setting circuit variably sets the level of the pair of bias pulses according to transmission conditions, whereby the operating point of the drive circuit is variably set. According to this configuration, amplification can be performed under desired operating conditions.

Preferably, the driving power supply includes a driving power supply connected to the driving circuit, wherein the driving power supply variably sets a voltage of the driving power supply according to a transmission condition, thereby outputting the driving power supply from the driving circuit. The transmission signal level is variably set.

(2) To achieve the above object,
The present invention provides a bias setting circuit that outputs a pair of bias pulses having bipolar symmetry having pulse widths corresponding to a plurality of original transmission signals, and an operation period and an operation point are determined by the pair of bias pulses. , A plurality of drive circuits for amplifying the original transmission signal, wherein the bias setting circuit is shared by the plurality of drive circuits.

According to this configuration, one bias circuit is provided for a plurality of drive circuits, so that the circuit configuration can be simplified. Preferably, the bias setting circuit has a pulse width that includes all of the plurality of original transmission signals.

(3) Incidentally, the above-mentioned bias pulse can also be called a pedestal clamp pulse. In this case, the bias setting circuit corresponds to a pedestal clamp circuit. Since the operating point of the drive circuit is fixed in the linear operation region only during the period of the pulse, it can be called a pseudo linear amplifier.

Therefore, according to the present invention, the problem of heat generation in the transmission circuit can be solved and the transmission circuit can be mounted with high density, and the device can be downsized. By operating the drive circuit as a high-speed negative feedback amplifier, an arbitrary waveform such as a pulse wave, a sine wave, and a Gaussian wave can be amplified at a low distortion rate.

Even if the high-voltage power supply supplied to the drive circuit is varied, the operating point of the circuit can be maintained at a predetermined value by the pedestal clamp pulse, so that the B mode, Doppler (CW) mode, CFM (color) (Flow mapping)
By setting the high-voltage power supply in each mode such as the mode to an appropriate value, it is possible to minimize the power consumption of the transmission circuit.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a transmission circuit used in an ultrasonic diagnostic apparatus. In FIG. 1, in this embodiment, a pair of pedestal clamp circuits 30 and a pseudo linear amplifier 32 are provided for each transducer (or transmission signal).

The pedestal clamp circuit 30 transmits a transmission control signal in consideration of a transmission focusing and a standby time for converging an ultrasonic beam from a control unit (not shown).
A PD is input, and pedestal clamp pulses Vb1 and Vb2 having positive / negative symmetry are generated based on the PD and transmitted to the pseudo linear amplifier 32. 5A to 5C show the transmission control signal PD and the pedestal clamp pulses Vb1 and Vb2.
Is exemplified. Here, the transmission control signal PD and the pedestal clamp pulses Vb1 and Vb2
Has a period that is longer before and after the entire period 100 of the original transmission waveform shown in FIG. 5E, that is, rises before the start point of the original transmission waveform by the period 102, and ends at the end of the original transmission waveform. It is set so as to fall later by the period 104 than the point.

The quasi-linear amplifier 32 is a drive circuit having a complementary symmetrical circuit configuration in which no input and output are DC-coupled in all stages and has no bias, and the power consumption when there is no signal is zero (0). The quasi-linear amplifier 32 operates as a high-speed negative feedback amplifier with the operating point of the circuit fixed in the linear operation region only during the generation period of the pedestal clamp pulse by the pedestal clamp pulses Vb1 and Vb2 sent from the pedestal clamp circuit 30. , An arbitrary waveform signal (original transmission signal) for driving the ultrasonic probe input in synchronization with the transmission control signal PD (Tx in)
Is linearly amplified, and Tx out is sent to a vibrator (not shown). FIG. 5D shows the original transmission waveform as described above,
FIG. 5E shows the waveform of the output signal Tx out.

Tx in is an arbitrary waveform such as a pulse wave, a sine wave, and a Gaussian wave that takes into account transmission focusing, transmission level, and transmission weighting (apodization) transmitted from a control unit (not shown).
It is generated in synchronization with PD.

Tx out is set such that the pseudo linear amplifier 32 outputs Tx in during the generation of the pedestal clamp pulses Vb1 and Vb2.
Is an output signal obtained by linearly amplifying the output signal, which is output to a vibrator (not shown).

In FIG. 1, Vcc and Vee are the power supplies of the pedestal clamp circuit 30, for example, ± 5
A predetermined voltage value within ± 15V is used. HV1 and HV2
Is a high-voltage power supply of the pseudo linear amplifier 32, which has positive and negative symmetrical voltage values, and can be variably set within a range of ± 10V to ± 100V automatically or manually according to a display mode or the like.

Therefore, when the drive circuit is constituted by the pseudo linear amplifier 32, the power consumption of the drive circuit when there is no signal can be reduced to zero (0), so that the problem of heat generation in the transmission circuit can be solved and the pedestal clamp pulse can be eliminated. Can be operated as a high-speed negative feedback amplifier only during the period of occurrence of high frequency, high-speed operation, high-speed response, low waveform distortion rate and circuit stabilization, and variable high-voltage power supply to the drive circuit However, since the operating point can be maintained at a predetermined value by the pedestal clamp pulse, the high-voltage power supply in each mode such as the B mode, the Doppler (CW) mode, and the CFM (color flow mapping) mode is set to an appropriate value. The power consumption of the drive circuit and the high-voltage power supply is minimized, and arbitrary waveforms such as pulse waves, sine waves, and The input wave waves or the like to amplify linearly a predetermined value at a low strain rate, can be driven (not shown) oscillator.

FIG. 2 is a schematic configuration diagram showing a transmission circuit according to another embodiment. 2, the pedestal clamp circuit 34 includes a plurality of pseudo linear amplifiers B1 to B48.
Connected in common.

Similarly to the above, the pedestal clamp circuit 34 generates positive and negative symmetric pedestal clamp pulses Vb1 and Vb2 from a control unit (not shown) based on the transmission control signal PD1 in consideration of the transmission focusing for converging the ultrasonic beam and the standby time. Then, they are sent to the pseudo linear amplifiers B1 to B48.

The pseudo linear amplifiers B1 to B48 are, similarly to the above, drive circuits each composed of a non-biased complementary symmetric circuit in which all input / output stages are DC-coupled, and the power consumption when there is no signal is zero.
(0). The quasi-linear amplifiers B1 to B48 use the pedestal clamp pulses Vb1 and Vb2 sent from the pedestal clamp circuit 34 to fix the operating point of the circuit to the linear operation region only during the period of generation of the pedestal clamp pulse, and to perform high-speed negative feedback amplification. Operates as a transmission control signal
Linearly amplify the ultrasonic probe driving arbitrary waveform signal Tx in1 to Tx in48 input in synchronization with PD1, and Tx out1 to Tx out48
To a vibrator (not shown). Where Vcc, Vee,
HV1 and HV2 are the same as those in the above-described embodiment, and a description thereof will be omitted.

Therefore, the pedestal clamp circuits can be grouped for each transmission focusing group, so that the cost of the transmission circuit can be reduced.

FIGS. 3 and 4 show specific circuit configuration examples of the pseudo linear amplifier shown in FIGS. 1 and 2. FIG.

First, in FIG. 3, Q1 to Q14 are transistors, R1 to R24 are resistors, and C1 to C3 are capacitors. This circuit includes a complementary symmetric current mirror circuit including resistors R1 to R14 and transistors Q1 to Q8, a floating shunt regulator circuit including resistors R15 to R17 and transistors Q9 and Q9, resistors R18 to R22, and capacitors C2 and C3. And a complementary symmetric single-ended push-pull circuit composed of transistors Q11 to Q14, and a feedback circuit having resistors R23 and R24 and a capacitor C1. In this circuit, the power consumption when there is no signal is zero (0) due to the zero bias in the input / output all-stage DC coupling. Hereinafter, the operation will be described in detail.

Based on the transmission control signal, pedestal clamp pulses Vb1 and Vb2 are generated and sent to both ends of the transmission control signal input terminals R2 and R3 of the pseudo linear amplifier. Then, the resistors R1 to R14 and the transistor Q
The operating point of the positive-negative symmetric complementary symmetric current mirror circuit composed of 1 to Q8 is fixed to AB1 class.

When the operating point of the positive-negative symmetric complementary symmetric current mirror circuit composed of the transistors Q1 to Q8 is fixed to the class AB1, the transistor based on the voltage generated at the resistors R15 and R16 by the collector current of the transistors Q7 and Q8. Q10
The transistor Q11 of the next stage is connected to the collector and the emitter of
A voltage for fixing the operating point of the complementary symmetric single-ended push-pull circuit consisting of .about.Q14 to class AB1 is transmitted.

With this voltage, the operating point of the complementary symmetric single-ended push-pull circuit including the transistors Q11 to Q14 is fixed to the class AB1. Here, capacitor C2,
C3 is for phase correction, and a value of several pF to several tens pF is used.

By the above procedure, the operating point of the drive circuit which is bias-free by DC coupling in all stages of input and output is fixed.
By the feedback circuit composed of R23, R24 and capacitor C1,
Negative feedback is applied to the input and output, resulting in a high-speed negative feedback amplifier with input and output in-phase. Here, the capacitor C1 is for phase correction, and is several pF
Is used.

The amplification factor Av of the circuit is expressed by the following equation.

Av = R24 / R23 The pedestal clamp pulses are set to Vb1 and Vb2 having positive and negative symmetry.
By making the above all-stage positive-negative symmetric complementary circuit,
Spike noise at the time of transient response of rising and falling of the pedestal clamp pulse can be suppressed. The effect of suppressing spike noise during transient response is
The same applies when the high-voltage power supplies HV1 and HV2 are varied when there is no input signal.

In a general linear amplifier, the drive circuit
The circuit consisting of Q1 to Q8 is composed of a differential amplifier circuit, the operating point when there is no signal is Class A, and the bias current when there is no signal is several hundred mA.
It is. Since tens to hundreds of drive circuits are used, heat generation is a problem.

Although not shown, at the time of reception for amplifying the reflected wave in the living body, since the linear amplifier is operating, noise generated from the linear amplifier becomes a problem from the viewpoint of SNR.

In the circuit of the present embodiment, since the drive circuit has an input / output all-stage DC coupling no-bias circuit configuration, the power consumption when there is no signal is zero (0). No problem. Further, in this embodiment, the drive circuits Q1 to Q8 are composed of positive and negative symmetric complementary symmetric current mirror circuits, and the operating point is fixed to the AB1 class by the pedestal clamp pulse. Since it is several tenths when there is no class bias signal, it also works thermally favorably at the time of transmission for driving a vibrator (not shown).

Next, an example of the circuit configuration of FIG. 4 will be described.
In FIG. 4, Q1 to Q12 are transistors, R1 to R19 are resistors, and C1 to C3 are capacitors. This circuit consists of resistors R1
A complementary symmetric current mirror circuit composed of R10 and transistors Q1 to Q6, resistors R11 to R13 and transistor Q7,
Floating type shunt regulator circuit consisting of Q8,
Resistors R14 to R18, capacitors C2 and C3 and transistor Q9
It consists of a complementary symmetric single-ended push-pull circuit consisting of ~ Q12, a feedback circuit consisting of a resistor R19 and a capacitor C1, with no input / output DC-coupled bias, and zero power consumption when there is no signal. . Hereinafter, the operation will be described in detail.

When pedestal clamp pulses Vb1 and Vb2 are generated based on the transmission control signal and sent out to both ends of the transmission control signal input terminals R2 and R3 of the pseudo linear amplifier, the resistors R1 to R10 and the transistor Q1 are output. ~ Q6
The operating point of the positive-negative symmetric complementary symmetric current mirror circuit is fixed to the AB1 class. The operating point of the positive / negative symmetric complementary symmetric current mirror circuit composed of the transistors Q1 to Q6 is
When fixed to class AB1, the collector and emitter of transistor Q8 are based on the voltage generated at the resistors R11 and R12 by the collector currents of transistors Q5 and Q6, and the complementary symmetric single-ended type consisting of transistors Q9 to Q12 in the next stage A voltage that fixes the operating point of the push-pull circuit to class AB1 is transmitted.

With this voltage, the operating point of the complementary symmetric single-ended push-pull circuit including the transistors Q9 to Q12 is fixed to the class AB1. Here, capacitor C2,
C3 is for phase correction and is about several pF to several tens pF.

With the above procedure, when the operating point of the input / output DC-coupled bias-free drive circuit is fixed, the resistors R1,
Negative feedback is applied to the input and output by the feedback circuit composed of R19 and the capacitor C1, thereby providing a high-speed negative feedback amplifier having input and output phases opposite to each other. Here, the capacitor C1 is for phase correction, and is of the order of several pF. The amplification factor Av of the circuit is expressed by the following equation.

Av = − (R19 / R1) By setting the pedestal clamp pulses to Vb1 and Vb2 having positive / negative symmetry and making the input / output all-stage DC-coupled no-bias drive circuit a complementary circuit having the above-mentioned positive / negative symmetry for all stages Thus, spike noise at the time of transient response of the rising and falling of the pedestal clamp pulse can be suppressed. Other operations are the same as those in FIG.

As described above, according to the above configuration,
The drive circuit is composed of a quasi-linear amplifier, and the problem of heat generation is eliminated by setting the power consumption when there is no signal to zero (0), and as a high-speed negative feedback amplifier only during the pedestal clamp pulse generation period. By operating, an input wave such as a pulse wave, a sine wave, and a Gaussian wave can be linearly amplified to a predetermined value, and a vibrator (not shown) can be driven.

Since the coupling capacitor is not used for the bias of the drive circuit, the recovery time for the transient response is extremely short, and the input / output symmetrical complementary circuit of all stages is used. Generation of spike noise can be effectively suppressed. Furthermore, since a transformer is not used, miniaturization by high-density mounting of circuits, integration of circuits into an integrated circuit, and the like are easy and cost can be reduced.

[0068]

As described above, according to the present invention,
Since the power consumption of the drive circuit when there is no signal can be reduced to zero, the problem of heat generation can be solved, and an advantage that an arbitrary waveform can be amplified can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission circuit according to the present invention.

FIG. 2 is a block diagram of a transmission circuit according to another embodiment.

FIG. 3 is a circuit diagram illustrating a configuration example of a drive circuit.

FIG. 4 is a circuit diagram showing another configuration example of the drive circuit.

FIG. 5 is a diagram showing waveforms of respective signals in the circuit.

FIG. 6 is a diagram showing an example of a conventional circuit configuration.

FIG. 7 is a diagram showing another conventional circuit configuration example.

[Explanation of symbols]

30 pedestal clamp circuit (bias setting circuit),
32 Pseudo linear amplifier (drive circuit).

Claims (10)

[Claims] A bias setting circuit for outputting a pair of biasing pulses having a pulse width corresponding to an original transmission signal and having bipolar symmetry; an operating period and an operating point are determined by the pair of biasing pulses; A transmission circuit for an ultrasonic diagnostic apparatus, comprising: a drive circuit for amplifying the original transmission signal. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the drive circuit has a circuit for supplying a bias current only for a period corresponding to a pulse width of the pair of bias pulses. Transmission circuit. 3. The transmission circuit according to claim 1, wherein the pair of bias pulses rise before a start point of the original transmission signal by a standby time. circuit. 4. The transmission circuit according to claim 1, wherein said drive circuit has a circuit for fixedly setting an operating point in a linear amplification region according to a level of said pair of bias pulses. The transmission circuit of the ultrasound diagnostic device. 5. The ultrasonic diagnostic apparatus according to claim 1, wherein the drive circuit has a complementary symmetric circuit configuration in which all stages from input to output are DC-coupled. Transmission circuit. 6. The transmission circuit according to claim 1, wherein the drive circuit is a negative feedback amplifier. 7. The transmission circuit according to claim 1, wherein the bias setting circuit variably sets a level of the pair of bias pulses according to a transmission condition, thereby variably setting an operating point of the drive circuit. A transmission circuit for an ultrasonic diagnostic apparatus, comprising: 8. The transmission circuit according to claim 1, further comprising a drive power supply connected to the drive circuit, wherein the drive power supply variably sets a voltage of the drive power supply according to a transmission condition. The transmission circuit of the ultrasonic diagnostic apparatus, wherein the level of the transmission signal output from the drive circuit is variably set. 9. A bias setting circuit for outputting a pair of bias pulses having a bipolar symmetry having a pulse width corresponding to a plurality of original transmission signals, and an operation period and an operation point are determined by the pair of bias pulses. And a plurality of drive circuits for amplifying the original transmission signal, wherein the bias setting circuit is shared by the plurality of drive circuits. 10. The transmission circuit according to claim 9, wherein said bias setting circuit has a pulse width that includes all of said plurality of original transmission signals.