JPH0653113B2 - Transmission circuit of ultrasonic diagnostic equipment - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a transmission circuit of an ultrasonic diagnostic apparatus.

[Technical Background of the Invention] In recent years, miniaturization of ultrasonic diagnostic apparatuses has been rapidly progressing.

The miniaturization of the device is very important in terms of easiness of movement of the device, reduction of occupied area, easy handling, and the like. However, in order to downsize the device, it is essential to downsize the electronic circuit device used in the device.

Here, in order to miniaturize the electronic circuit device, it is desirable to collectively miniaturize the circuit blocks in as wide a range as possible. For that reason, hybrid ICs and monolithic ICs of circuit blocks are currently generally used.

By the way, the hybrid IC is, for example, a bare chip transistor, a mi-molded transistor, a chip resistor and the like arranged on an alumina substrate and wired.

A monolithic IC is made by simultaneously forming a large number of transistors, resistors and the like in a silicon single crystal of several mm square.

Therefore, the monolithic IC is essentially advantageous over the hybrid IC in terms of high-density mounting (circuit miniaturization).

However, at present, the monolithic IC is a hybrid I.
Compared with C (or a circuit composed of discrete components), there are great restrictions in electronic circuit design.

For example, a switching transistor for large current, high breakdown voltage, and high speed processing is not made into a monolithic IC, and it is difficult at present to make a PNP transistor capable of passing a current of several hundred mA or more.

Originally, monolithic ICs have been developed for so-called digital circuits. Therefore, ingenuity of the circuit itself is indispensable in order to realize a monolithic IC suitable for large current, high breakdown voltage, and high-speed processing.

Now, the transmission circuit of the ultrasonic diagnostic apparatus is a circuit for generating a transmission pulse for driving the ultrasonic transducer.

A conventional example of such a transmission circuit will be described with reference to the second example.

The transmission circuit shown in the figure has an input pulse P with a peak value of about 5V.
An output pulse POUT is output to a drive circuit unit 1 that inputs IN and an ultrasonic probe (not shown) driven by this drive circuit unit 1.
P-channel FET (normal power MOS
FET) and an output transistor Q3.

The drive circuit unit 1 clamps a push-pull emitter follower including an NPN transistor Q1 and a PNP transistor Q2 that realizes low output impedance, and a constant voltage pulse from the push-pull emitter follower to clamp a high voltage (100 to 200 V) pulse. (Drive pulse Pd)
To the output transistor Q3 for switching and driving the same, and a clamp circuit including a capacitor C1, a resistor R1 and a diode D. Incidentally, in FIG. 2, the capacitor C2 connected to the gate of the output transistor Q3 by a broken line is a parasitic capacitor which normally has a value of about 500 pF.

Also, a resistor R connected to the output stage of the output transistor Q3
2 may be replaced by a FET.

Next, the output pulse POU output from the transmission circuit having the above configuration
The waveform of T is shown in FIG.

The pulse amplitude of this output pulse is several 10 V to 200 V, the pulse width is 50 ns to 200 ns, and the repetition period is 80 μs.
It is 300 μs. Therefore, it takes about several tens of μs for the rise and fall times.

[Problems of Background Art] As described above, the transmission circuit of the ultrasonic diagnostic apparatus has a high withstand voltage,
Although various characteristics such as high speed switching are required, in the conventional transmission circuit shown in FIG. 2, the switching speed of the output transistor Q3 is deteriorated due to the presence of the capacitor C2.

When the drive circuit unit 1 is to be integrated into an IC, for example, a hybrid IC, the transistor Q1 and the transistor Q2 can be realized by a normal mini-mold transistor for high-speed switching, and the capacitor C1 can be realized by a chip capacitor. . However, if a monolithic IC is to be realized in order to realize a higher density IC, it is impossible to realize such an IC because of the existence of the PNP type transistor Q2 as described above. Monolithic IC with a condenser
It is difficult to convert. In particular, the capacitance value of the capacitor C1 is usually required to be several thousand pF or more, and it is impossible to make such a capacitor C1 into an IC.

Furthermore, if the transistor Q2, the capacitor C1 and the like are externally attached to the IC by discrete parts, the packaging density is lowered, and eventually the conventional transmission circuit shown in FIG. 2 requires some circuit technology countermeasure. .

[Object of the Invention] The present invention has been made in view of the above circumstances, and an ultrasonic diagnostic apparatus which does not require external parts, can be realized as a monolithic IC, enables high-density mounting, and is also excellent in high-speed switching characteristics. It is an object of the present invention to provide a transmitting circuit of the above.

[Outline of the Invention] An outline of the present invention for achieving the above object is to provide a drive circuit unit that converts a predetermined input pulse into a high-voltage pulse and sends the high-voltage pulse,
In a transmission circuit of an ultrasonic diagnostic apparatus, which is driven by switching by the high-voltage pulse and sends an output pulse for excitation to an ultrasonic probe, and an output transistor including a parasitic capacitor, the drive circuit section has a common input pulse. A collector including first and second grounded-ground amplifier circuits including input NPN transistors, and NPN transistors driven by the first grounded-ground amplifier circuit and having an output terminal common to the second grounded-ground amplifier circuit. The second base-grounded amplifier circuit is configured to discharge the charge stored in the parasitic capacitor.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG.
In the transmission circuit shown in the figure, those having the same functions as those of the conventional transmission circuit shown in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The circuit shown in FIG.
The difference from the one shown in the figure is that the drive circuit section 10 includes first and second base-grounded amplifier circuits composed of NPN transistors Qa and Qb having resistors Ra and Rb respectively connected to the input side and the first base. N driven by a ground amplifier circuit and having its output terminal connected to the gate of the output transistor Q3 together with the output terminal of the second grounded base amplifier circuit.
And a grounded collector amplifier circuit (emitter follower) composed of a PN transistor Qc, and a capacitor C1.
And the diode D is omitted.

In FIG. 1, Rc is a resistor connected between the power source + Vh and the base of the NPN transistor Qc.

The drive circuit section 10 of the transmission circuit configured as described above has excellent high frequency characteristics because the grounding method is base grounding and collector grounding (emitter follower).

Further, the charge of the capacitor C2 is charged through the NPN transistor Qc, and the charge of the second base-grounded amplifier circuit is N.
Since the NPN transistor Qc is switched by the NPN transistor Qa while being discharged through the PN transistor Qb, the potential of the drive pulse Pd 'sent to the output transistor Q3 is (Rc × 5 / Ra) volts ( It is usually expressed as 100 to 200 volts) and follows the input pulse PIN of this circuit well.

Further, the rising characteristic of the drive pulse Pd 'to the output transistor Q3 has good high frequency characteristics, and the NPN transistor Qc has a good high frequency characteristic.
Is improved by the transistor Qb having good high frequency characteristics.

Therefore, if the waveform of the input pulse PIN is sufficiently good (this can be easily realized because it is usually at a low voltage level), the drive pulse P to the output transistor Q3 is obtained.
d'can be made sufficiently good without being affected by the capacitor C2.

The transmission circuit having the above-described configuration and operation is expressed by the formula 10
Since it has a high breakdown voltage of 0 V or more, good high frequency characteristics, and does not include a capacitor, it has excellent high-speed switching characteristics, is suitable for a monolithic IC, and realizes high-density mounting of a transmission circuit.

Needless to say, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist thereof.

[Effects of the Invention] According to the present invention described in detail above, since the drive circuit section is composed of the grounded base amplifier circuit and the grounded collector amplifier circuit, external parts are not required, and a monolithic IC can be realized, and the circuit as a whole can be improved. It is possible to provide a transmission circuit of an ultrasonic diagnostic apparatus that can be densely packed and has excellent high-speed switching characteristics.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional transmission circuit, and FIG. 3 is a waveform diagram showing output pulses of the transmission circuit. 10 ... Driving circuit section, Qa, Qb, Qc ... NPN transistor, Q3 ... Output transistor.

Claims (2)

[Claims] 1. A drive circuit section for converting a predetermined input pulse into a high-voltage pulse and transmitting the same, and an output transistor including a parasitic capacitor for transmitting an output pulse for excitation to an ultrasonic probe which is switching-driven by the high-voltage pulse. In the transmission circuit of the ultrasonic diagnostic apparatus having :, the drive circuit unit is an NPN to which an input pulse is commonly input.
Grounded first and second base amplification circuit including a transistor, and grounded collector amplification circuit including an NPN transistor driven by the first grounded base amplification circuit and having an output terminal common to the second grounded base amplification circuit A transmission circuit of an ultrasonic diagnostic apparatus, characterized in that the second base-grounded amplification circuit is configured to discharge the charge of the parasitic capacitor. 2. The transmission circuit of the ultrasonic diagnostic apparatus according to claim 1, wherein the drive circuit unit is integrated.