TWO-TERMINAL SEMICONDUCTOR SENSOR DEVICE

• US 20100054302A1
• Filed: 08/24/2009
• Published: 03/04/2010
• Est. Priority Date: 08/29/2008
• Status: Active Grant

• Current Assignee: Ablic Inc. (MinebeaMitsumi Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: ANZAI, Ryoichi
• Granted Patent: US 8,403,559 B2
• Time in Patent Office: Days
• US Class Current: 374/178
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

Provided is a two-terminal semiconductor sensor device with which an external device having low circuit or element accuracy may be used. An output voltage (VOUT) of the two-terminal semiconductor sensor device based on temperature is not based on a constant current of a constant current source (70) of the external device and a current of an output transistor (60) of the two-terminal semiconductor sensor device, but on a resistance ratio of a voltage dividing circuit including a resistor (30) and a resistor (40), and a temperature voltage (Vbe) of the two-terminal semiconductor sensor device. Accordingly, accuracy of the constant current of the constant current source (70) of the external device that receives the output voltage (VOUT) does not need to be high. Therefore, the external device does not need to have a highly accurate circuit or element for receiving the output voltage (VOUT).

Claims

1. A two-terminal semiconductor sensor device to be connected to an external device through two terminals, comprising:

a first external terminal to be connected to a ground potential that is common to the external device;

a second external terminal for receiving an operating current from the external device;

a sensor circuit for measuring one physical amount to output a voltage based on the one physical amount;

a voltage dividing circuit for dividing a voltage between the first external terminal and the second external terminal to output a divided voltage;

a differential amplifier circuit for receiving the voltage output from the sensor circuit and the divided voltage to output a voltage based on a difference therebetween; and

an output transistor having a gate connected to an output terminal of the differential amplifier circuit, a drain connected to one of the first external terminal and the second external terminal, and a source connected to another one of the first external terminal and the second external terminal.

2. A two-terminal semiconductor sensor device according to claim 1, wherein the one physical amount comprises temperature.

3. A two-terminal semiconductor sensor device according to claim 2, wherein the sensor circuit comprises:

a constant current circuit for supplying a constant current; and

a temperature detecting circuit for receiving the constant current to output a voltage based on the temperature.

4. A two-terminal semiconductor sensor device according to claim 3, wherein the temperature detecting circuit comprises a bipolar transistor having a base and a collector, which are connected to the first external terminal, and an emitter connected to an output terminal of the sensor circuit.

5. A two-terminal semiconductor sensor device according to claim 3, wherein the temperature detecting circuit comprises:

a first bipolar transistor having a base and a collector, which are connected to the first external terminal;

a second bipolar transistor having a base connected to an emitter of the first bipolar transistor, and a collector connected to the first external terminal; and

a third bipolar transistor having a base connected to an emitter of the second bipolar transistor, an emitter connected to an output terminal of the temperature detecting circuit, and a collector connected to the first external terminal.

6. A two-terminal semiconductor sensor device according to claim 2, wherein the sensor circuit comprises:

a first bipolar transistor having a base and a collector, which are connected to the first external terminal;

a second bipolar transistor having a base and a collector, which are connected to the first external terminal;

a first resistor having one terminal connected to an emitter of the first bipolar transistor;

a differential amplifier circuit having an input terminal connected to another terminal of the first resistor, and another input terminal connected to an emitter of the second bipolar transistor;

a current mirror circuit for outputting a current based on a voltage at an output terminal of the differential amplifier circuit from a plurality of output terminals, of which a first output terminal outputs the current to the first resistor and the first bipolar transistor, a second output terminal outputs the current to the second bipolar transistor, and a third output terminal outputs the current to the second resistor; and

a second resistor having one terminal connected to the first external terminal, and another terminal serving as an output terminal of the sensor circuit.