Receiving circuit, semiconductor device, and sensor device

Patent metadata

Field	Value
Publication number	US-9429646-B2
Application number	US-201214342578-A
Country	US
Kind code	B2
Filing date	Aug 31, 2012
Priority date	Sep 7, 2011
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A receiving circuit ( 10 ) includes an amplifier ( 15 ) which amplifies receiving signals (SP, SN) of a piezoelectric sensor ( 2 ), and a plurality of transistors ( 11 a , 11 b ) or ( 12 a, 12 b ), which are connected in parallel to between one end of the piezoelectric sensor ( 2 ) and one end of the amplifier ( 15 ), and are turned on with phase shift when switching is performed to receiving operations.

First claim

The invention claimed is:

1. A receiving circuit comprising:
an amplifier for amplifying a reception signal of a piezoelectric sensor; and
a plurality of transistors connected in parallel between one end of the piezoelectric sensor and one end of the amplifier, the transistors being turned on with phase shift in switching to a reception operation.

2. The receiving circuit according to claim 1 , wherein the plurality of transistors are 2n transistors obtained by dividing a single transistor having desired impedance characteristics into ½n (n is a natural number).

3. The receiving circuit according to claim 2 , wherein the 2n transistors are turned on with phases shifted by T/2n each (T is a resonance period of the piezoelectric sensor) in switching to the reception operation.

4. The receiving circuit according to claim 1 , further comprising a filter for blunting a control signal of each transistor.

5. The receiving circuit according to claim 1 , wherein the reception signal is transmitted between the piezoelectric sensor and the amplifier in a differential form.

6. The receiving circuit according to claim 5 , further comprising a switch for short-circuiting a positive phase transmission path and a reverse phase transmission path of the reception signal in switching to the reception operation.

7. A receiving circuit comprising:
an amplifier for differentially amplifying a reception signal of a piezoelectric sensor;
a first transistor for connecting between the piezoelectric sensor and the amplifier in switching to a reception operation; and
a second transistor for short-circuiting a positive phase transmission path and a reverse phase transmission path of the reception signal in switching to the reception operation.

8. A receiving circuit comprising:
an amplifier for amplifying a reception signal of the piezoelectric sensor;
a main transistor connected between one end of the piezoelectric sensor and one end of the amplifier, the main transistor being turned on in switching to a reception operation; and
a sub transistor connected in parallel to the main transistor, the sub transistor having a larger on-impedance than the main transistor and being turned on prior to the main transistor in switching to the reception operation.

9. The receiving circuit according to claim 8 , the main transistor is divided into 2n transistors to be turned on with phases shifted by T/2n each (T is a resonance period of the piezoelectric sensor, and n is a natural number) in switching to the reception operation.

10. The receiving circuit according to claim 8 , further comprising a filter for blunting control signals of the main transistor and the sub transistor.

11. The receiving circuit according to claim 8 , wherein the reception signal is transmitted between the piezoelectric sensor and the amplifier in a differential form.

12. The receiving circuit according to claim 11 , further comprising a switch for short-circuiting a positive phase transmission path and a reverse phase transmission path of the reception signal in switching to the reception operation.

13. A semiconductor device, comprising the receiving circuit according to claim 1 , to which the reception signal is input from the piezoelectric sensor.

14. The semiconductor device according to claim 13 , further comprising:
a transmission circuit configured to output a transmission signal to the piezoelectric sensor; and
a control circuit configured to control the reception operation of the receiving circuit and the transmission operation of the transmission circuit in a time sharing manner.

15. The semiconductor device according to claim 14 , wherein
the transmission circuit is disposed for each one of a plurality of piezoelectric sensors, and
the receiving circuit is disposed solely for the plurality of piezoelectric sensors.

16. The semiconductor device according to claim 11 , wherein a plurality of signal paths respectively connecting between the receiving circuit and the plurality of piezoelectric sensors are designed to have the same length.

17. A sensor device comprising a piezoelectric sensor and the semiconductor device according to claim 13 .

18. The sensor device according to claim 17 , wherein the sensor device is a current meter for measuring flow speed of a fluid flowing in a pipe.

19. The sensor device according to claim 18 , wherein the piezoelectric sensor includes a first piezoelectric sensor and a second piezoelectric sensor disposed on an inner wall surface of the pipe in such a manner to be opposed to each other with a predetermined angle to the fluid.

20. The receiving circuit according to claim 9 , further comprising a filter for blunting control signals of the main transistor and the sub transistor.

Assignees

• Niwa Isao
• Noguchi Youichiro
• Rohm Co Ltd

Inventors

• Niwa Isao
• Noguchi Youichiro

Classifications

• G01S7/52017

  particularly adapted to short-range imaging (G01S7/53 takes precedence) · CPC title

• G01S7/523

  Details of pulse systems {(short-range imaging G01S7/52017; methods or devices for transmitting, conducting or directing sound G10K11/18)} · CPC title

• G01S7/526 Primary

  Receivers · CPC title

• G01F1/667 Primary

  Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters · CPC title

• G01S15/931

  of land vehicles · CPC title