Ultrasonic diagnostic apparatus and probe used for the same
Provided is a probe which transmits an ultrasonic wave to a diagnostic site and receives a reception signal which is a reflected wave. The probe includes: a plurality of transducers; a plurality of low-noise amplifying circuits respectively corresponding to the plurality of transducers; and a single differential converter which converts a control signal rising with the elapse of time to a first bias signal rising with the elapse of time and a second bias signal falling with the elapse of time to control the plurality of low-noise amplifying circuits, and the low-noise amplifying circuit includes an attenuator which attenuates: an electric signal from the transducer; a first amplifying circuit which sets the first bias signal as a bias and amplifies an output signal of the attenuator to be gradually increased with the elapse of time; a second amplifying circuit which sets the second bias signal as a bias and amplifies the output signal of the attenuator to be gradually reduced with the elapse of time; and a subtractor which subtracts an output of the first amplifying circuit and an output of the second amplifying circuit.
1. A probe used for an ultrasonic diagnostic apparatus, the probe configured to transmit an ultrasonic wave to a diagnostic site, receive a reception signal which is a reflected wave and obtain information necessary for diagnosis based on the reception signal, the probe comprising:
a plurality of transducers;
a plurality of low-noise amplifying circuits each corresponding to one of the plurality of transducers; and
a single differential converter which converts a control signal rising with an elapse of time to a first bias signal rising with the elapse of time and a second bias signal falling with the elapse of time to control the plurality of low-noise amplifying circuits, wherein
each of the low-noise amplifying circuits includes
an attenuator which attenuates an electric signal from a respective transducer of the plurality of transducers,
a first amplifying circuit which sets the first bias signal as a bias and amplifies an output signal of the attenuator to be gradually increased with the elapse of time,
a second amplifying circuit which sets the second bias signal as a bias and amplifies the output signal of the attenuator to be gradually reduced with the elapse of time, and
a subtractor which subtracts an output of the first amplifying circuit and an output of the second amplifying circuit;
the first amplifying circuit and the second amplifying circuit are first and second cascode-connected differential amplifying circuits and realize the subtractor by being connected after switching polarities of respective outputs;
the attenuator is constituted by series-connecting a resistor and a transistor; and
a bias voltage of the tail current source of the second cascode-connected differential amplifying circuit and a bias voltage of the transistor constituting the attenuator are shared.
2. The probe according to claim 1 , wherein
during an operation period, the first bias signal is always greater than the second bias signal.
3. The probe according to claim 1 , wherein
using the second bias signal, an attenuation degree of the attenuator is reduced with the elapse of time.
4. The probe according to claim 1 , further comprising:
a constant current generation circuit for generating the control signal by charging a capacitor with a constant current.
5. The probe according to claim 4 , wherein
the constant current generation circuit has a function of discharging the capacitor and a function of fixing the capacitor to a power supply voltage.
6. The probe according to claim 4 , wherein
the constant current generation circuit has a function capable of disconnecting the capacitor.
7. The probe according to claim 4 , wherein
the constant current generation circuit has a function capable of varying a constant current value for charging the capacitor.
8. The probe according to claim 1 , wherein
the first bias signal is constant during the elapse of time.
9. The probe according to claim 1 , wherein
the single differential converter can vary a gain by varying the second bias signal.
10. The probe according to claim 1 , wherein
a signal not attenuating with the attenuator turned off is supplied to the first amplifying circuit and the second amplifying circuit.
11. The probe according to claim 1 , wherein
the first amplifying circuit and the second amplifying circuit can be used as fixed gain amplifiers.
12. The probe according to claim 1 , wherein
the first bias signal and the second bias signal are respectively tail current sources of the first and second cascode-connected differential amplifying circuits.
13. The prove according to claim 1 , wherein
the single differential converter and the plurality of low-noise amplifying circuits are constituted of one semiconductor circuit and the plurality of low-noise amplifying circuits are commonly controlled by the first bias signal and the second bias signal in the single differential converter.
14. The probe according to claim 1 , wherein
the single differential converter and the plurality of low-noise amplifying circuits are constituted of a plurality of semiconductor circuits and the plurality of low-noise amplifying circuits are commonly controlled by the first bias signal and the second bias signal in the single differential converter, and
the control signal is shared by the plurality of semiconductor circuits.
15. An ultrasonic diagnostic apparatus comprising:
a probe for transmitting an ultrasonic wave to a diagnostic site and receiving a reception signal which is a reflected wave; and
a signal processing circuit for obtaining information necessary for diagnosis based on the reception signal, wherein
the probe includes a plurality of transducers, a plurality of low-noise amplifying circuits respectively corresponding to the plurality of transducers, and a single differential converter which converts a control signal rising with the elapse of time to a first bias signal rising with the elapse of time and a second bias signal falling with the elapse of time to control the plurality of low-noise amplifying circuits, and
each of the low-noise amplifying circuits includes
an attenuator which attenuates an electric signal from a respective transducer of the plurality of transducers,
a first amplifying circuit which sets the first bias signal as a bias and amplifies an output signal of the attenuator to be gradually increased with the elapse of time,
a second amplifying circuit which sets the second bias signal as a bias and amplifies the output signal of the attenuator to be gradually reduced with the elapse of time, and
a subtractor which subtracts an output of the first amplifying circuit and an output of the second amplifying circuit;
the first amplifying circuit and the second amplifying circuit are first and second cascode-connected differential amplifying circuits and realize the subtractor by being connected after switching polarities of respective outputs;
the attenuator is constituted by series-connecting a resistor and a transistor; and
a bias voltage of the tail current source of the second cascode-connected differential amplifying circuit and a bias voltage of the transistor constituting the attenuator are shared.