Ultrasonic probe and ultrasonic diagnostic apparatus using thereon

1. An ultrasonic probe transmitting an ultrasonic wave to a diagnostic organ and receiving a reception signal that is a reflected wave, the ultrasonic probe comprising:

a plurality of transducers;

a plurality of low-noise amplifier circuits individually corresponding to the plurality of transducers, wherein each of the plurality of low-noise amplifier circuits has a variable resistor negative feedback unit making a resistance value variable by a voltage signal inputted to a control terminal of the variable resistor negative feedback unit; and

a control circuit,

wherein the control circuit includes:

a dummy circuit generating a bias voltage of the variable resistor negative feedback unit in each of the plurality of the low-noise amplifier circuits; and

an adding circuit outputting an added signal generated by adding the bias voltage from the dummy circuit and a control signal increasing or decreasing with a lapse of time, and wherein

each of the plurality of low-noise amplifier circuits input an output of the adding circuit to the control terminal of the variable resistor negative feedback unit to perform variable control on a gain of the low-noise amplifier circuit,

the control circuit further includes a floating voltage circuit,

the floating voltage circuit has a variable resistor making a resistance value variable by an electrical signal inputted to a control terminal,

the floating voltage circuit feeds a direct current signal to the control terminal of the variable resistor and carries a direct current to the variable resistor to generate a floating voltage, and

the control circuit inputs a signal that has been level shifted by the floating voltage based on the added signal output of the adding circuit to the control terminal of the variable resistor negative feedback unit in each of the plurality of low-noise amplifier circuits.

2. The ultrasonic probe according to claim 1 , wherein the dummy circuit is composed of a dummy low-noise amplifier circuit and a dummy negative feedback resistor connected between an input and an output of the dummy low-noise amplifier circuit.

3. The ultrasonic probe according to claim 2 , wherein the dummy circuit is mounted on a semiconductor die the same as the plurality of low-noise amplifier circuits.

4. The ultrasonic probe according to claim 1 , wherein:

the variable resistor negative feedback unit is a first N-channel or a first P-channel field effect transistor, and the control terminal of the variable resistor negative feedback unit is a gate terminal of the first N-channel or the first P-channel field effect transistor;

the variable resistor of the floating voltage circuit is a second N-channel or a second P-channel field effect transistor having a gate connected to a drain, the direct current signal is fed to the second N-channel or the second P-channel field effect transistor, and a gate-to-source voltage of the second N-channel or the second P-channel field effect transistor is the floating voltage; and

the control circuit inputs the signal that has been level shifted by the floating voltage based on the added signal output of the adding circuit to the control terminal of the variable resistor negative feedback unit in each of the plurality of low-noise amplifier circuits.

5. The ultrasonic probe according to claim 4 , wherein:

the low-noise amplifier circuit is an operational amplifier;

the first N-channel or the first P-channel field effect transistor is a variable resistor applying negative feedback from an output of the operational amplifier to an inverting input terminal; and

a non-inverting input terminal of the operational amplifier is supplied with a reference voltage.

6. The ultrasonic probe according to claim 1 , wherein:

the low-noise amplifier circuit is a differential amplifier circuit having two field effect transistors arranged side by side; and

the variable resistor negative feedback unit is a third field effect transistor connected between sources of the two field effect transistors, and the variable resistor negative feedback unit inputs the output of the adding circuit to a gate of the third field effect transistor.

7. An ultrasonic probe transmitting an ultrasonic wave to a diagnostic organ and receiving a reception signal that is a reflected wave, the ultrasonic probe comprising:

a plurality of transducers;

a plurality of low-noise amplifier circuits individually corresponding to the plurality of transducers, wherein each of the plurality of low-noise amplifier circuits has a variable resistor negative feedback unit making a resistance value variable by a voltage signal inputted to a control terminal of the variable resistor negative feedback unit; and

a control circuit,

wherein the control circuit includes:

a dummy circuit generating a bias voltage of the variable resistor negative feedback unit in each of the plurality of the low-noise amplifier circuits; and

an adding circuit outputting an added signal generated by adding the bias voltage from the dummy circuit and a control signal increasing or decreasing with a lapse of time, and wherein

each of the plurality of low-noise amplifier circuits input an output of the adding circuit to the control terminal of the variable resistor negative feedback unit to perform variable control on a gain of the low-noise amplifier circuit,

the low-noise amplifier circuit is an inverter circuit having a first P-channel field effect transistor connected in series to a first N-channel field effect transistor,

the variable resistor negative feedback unit is a unit having a second N-channel field effect transistor connected in parallel to a second P-channel field effect transistor,

one end of the parallel connection of the second N-channel field effect transistor to the second P-channel field effect transistor is connected to a connecting point of the first P-channel field effect transistor to the first N-channel field effect transistor, and another end of the parallel connection is connected to gates of the first P-channel field effect transistor and the first N-channel field effect transistor,

a first added signal which is an output of the adding circuit outputting a sum of the bias voltage from the dummy circuit and a first control signal increasing or decreasing with a lapse of time and whose level is shifted by a gate-to-source voltage of a third N-channel field effect transistor is connected to a gate terminal of the second N-channel field effect transistor of the low-noise amplifier circuit,

a second added signal which is an output of the adding circuit outputting a sum of the bias voltage from the dummy circuit and a second control signal having a slope inverted to the first control signal with a lapse of time and whose level is shifted by a gate-to-source voltage of a third P-channel field effect transistor is connected to a gate terminal of the second P-channel field effect transistor of the low-noise amplifier circuit, and

by these connections, the gain of the low-noise amplifier circuit is variably controlled.

8. The ultrasonic probe according to claim 7 , comprising:

a constant current generating circuit generating a signal increasing or decreasing with a lapse of time by charging a capacitance with a constant current; and

a single differential signal converter circuit receiving a difference between the signal and a reference direct current signal to generate the first control signal and second control signal.

9. The ultrasonic probe according to claim 8 , wherein a gain of the single differential signal converter circuit is made variable to make the gain of the low-noise amplifier circuit variable.

10. The ultrasonic probe according to claim 8 , wherein the reference direct current signal is made variable to make the gain of the low-noise amplifier circuit variable.

11. The ultrasonic probe according to claim 1 , comprising a control signal generating circuit generating the control signal by charging a capacitance with a constant current.

12. The ultrasonic probe according to claim 11 , wherein the control signal generating circuit includes a function of discharging the capacitance and/or a function of fixing the capacitance to a power supply voltage.

13. An ultrasonic diagnostic apparatus comprising:

the ultrasonic probe according to claim 1 ; and

a signal processing circuit obtaining information necessary for diagnosis based on a reception signal of the ultrasonic probe.