Probe and ultrasound diagnostic device using the same

1. A probe that is connected to an ultrasound diagnostic apparatus, and is configured to transmit an ultrasound wave to a diagnostic site and receive a receive signal which is a reflected wave, the probe comprising:

a plurality of receive circuits, wherein

each of the receive circuits includes:

an ultrasound transducer that is configured to convert the receive signal into a ground level electric signal and output the electric signal as a first output signal;

a transmit/receive switch that is connected to a first signal line and is configured to switch depending on whether to output the first output signal output from the ultrasound transducer to the first signal line;

a variable attenuator that is provided with a control terminal and two terminals, and is configured to change a resistance value between the two terminals other than the control terminal based on a control signal input to the control terminal;

a first capacitor that is connected to the first signal line; and

an amplifier that has an input terminal connected to the first capacitor and includes at least an amplifier circuit configured to amplify an electric signal of the first signal line and output the amplified electric signal to a second signal line,

the transmit/receive switch is configured to output a bias potential to the first signal line when the transmit/receive switch is turned off, and

in the variable attenuator, one terminal of the two terminals other than the control terminal is connected to the first signal line, and another terminal is connected to the ground via a second capacitor different from the first capacitor.

2. The probe according to claim 1 , further comprising an integrated circuit and one or more common capacitors disposed outside the integrated circuit, wherein

the integrated circuit includes a plurality of the receive circuits,

the common capacitor is connected to the plurality of receive circuits and operates as the second capacitor of the plurality of receive circuits, and

the common capacitor is located outside the integrated circuit.

3. The probe according to claim 2 , wherein

an electrostatic capacitance of the common capacitor is larger than an electrostatic capacitance of the first capacitor.

4. The probe according to claim 2 , comprising:

one or more control signal generators configured to output the control signal to each of the plurality of receive circuits, wherein

the control signal generator is mounted in a region around a region where the plurality of receive circuits are mounted in the integrated circuit.

5. The probe according to claim 2 , wherein

two or more common capacitors are provided, and the common capacitors are respectively connected to the plurality of the receive circuits via two or more pads provided in the integrated circuit, and

each receive circuit is connected to a pad, among the two or more pads, which is at a position nearest to the receive circuit such that a length of a wiring line connected to the common capacitor is equal to or less than a predetermined value.

6. The probe according to claim 1 , wherein

an OFF state bias potential output to the first signal line when the transmit/receive switch is turned off is equal to an ON state bias potential output to the first signal line when the transmit/receive switch is turned on.

7. The probe according to claim 1 , wherein

the transmit/receive switch includes one or more MOSFETs, and has a function of causing a current for determining the bias potential of the first signal line to flow to the first capacitor side without passing through a high-breakdown-voltage MOSFET when the transmit/receive switch is turned off.

8. The probe according to claim 1 , wherein

the variable attenuator includes one or more MOSFETs including the control terminal and the two terminals, and

a back gate of the MOSFET is connected to a power supply that is not at a ground potential.

9. An ultrasound diagnostic apparatus comprising:

the probe according to claim 1 ; and

a processing device configured to process a signal received from the probe.

10. A probe that is connected to an ultrasound diagnostic apparatus, and is configured to transmit an ultrasound wave to a target site and receive an ultrasound signal which is a reflected wave, the probe comprising:

a plurality of arranged ultrasound transducers; a plurality of transmit circuits configured to respectively output transmit signals to the plurality of ultrasound transducers; and a plurality of receive circuits respectively connected to the plurality of ultrasound transducers, wherein

each of the plurality of receive circuits includes: a transmit/receive switch; an amplifier circuit; a first signal line connecting the transmit/receive switch to the amplifier circuit; and a variable attenuator connected to an intermediate portion of the first signal line,

the ultrasound transducers convert the ultrasound signal into an electric signal and output the electric signal to the transmit/receive switch as a first output signal,

the transmit/receive switch switches depending on whether to output the first output signal from the ultrasound transducer to the first signal line, and

the variable attenuator includes one or more elements, the element is an element in which a control terminal and two terminals are provided and a resistance value changes between the two terminals other than the control terminal according to a control signal input to the control terminal, and one of the two terminals of the element is connected to the first signal line.

11. The probe according to claim 10 , wherein

the one or more elements of the variable attenuator include an N-channel MOSFET and a P-channel MOSFET, the N-channel MOSFET and the P-channel MOSFET are connected in parallel, one terminal side of the parallel connected MOSFETs is connected to the first signal line, and another terminal side is connected to the ground via a second capacitor.

12. The probe according to claim 10 , wherein

the transmit/receive switch includes: one or more transmit/receive switch MOSFETs; a floating voltage generation unit; a switch element; a bypass signal line; and a resistor having one end connected to the first signal line,

one of a source terminal and a drain terminal of the transmit/receive switch MOSFET is connected to the ultrasound transducer, and another one of the source terminal and the drain terminal is connected to the first signal line,

the floating voltage generation unit generates a voltage to be applied between a gate and a source of the transmit/receive switch MOSFET,

the one end of the resistor is connected to the first signal line, and another end of the resistor is connected to the ground, and

the switch element includes: a switch terminal connected to a bias current source; an ON terminal; and an OFF terminal, the ON terminal is connected to the floating voltage generation unit and supplies a bias current to the floating voltage generation unit when the switch element is turned on, and the OFF terminal is connected to the first signal line via the bypass signal line and causes the bias current to flow into the resistor via the first signal line when the switch element is turned off.

13. The probe according to claim 10 , wherein

a first capacitor is inserted in series in the first signal line between the amplifier circuit and the transmit/receive switch.

14. An ultrasound diagnostic apparatus comprising:

the probe according to claim 10 ; and

a processing device configured to process a signal received from the probe.