Semiconductor device, temperature sensor, and electronic apparatus comprising it

• US 7,176,701 B2
• Filed: 03/10/2003
• Issued: 02/13/2007
• Est. Priority Date: 03/11/2002
• Status: Expired due to Fees

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Wachi, Takatsugu, Nakamura, Akira
• Primary Examiner(s): Hirshfeld; Andrew H.
• Assistant Examiner(s): He; Amy
• Application Number:
  US10/504,856
• Publication Number:
  US 20050104151A1
• Time in Patent Office: 1,436 Days
• Field of Search: 324/760, 324/721, 327/512, 327/513, 257/470, 374/178
• US Class Current: 324/721
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence
• CPC Class Codes: H03F 3/45085 Long tailed pairs H03F3/45112, H03F3/45139 take precedence

Abstract

A temperature sensor including two transistors having different emitter current densities and performing temperature detection based on the fact that the difference in voltage between base and emitter changes with temperature. The temperature sensor is provided with a feedback circuit for controlling respective collector voltages and emitter currents such that the collector voltages of both transistors vary according to similar temperature characteristics.

Claims

1. A temperature sensor comprising first and second transistors having different emitter current densities and a feedback circuit for controlling collector voltages and emitter currents of the first and second transistors such that the collector voltages of the first and second transistors vary with similar temperature responses, the temperature sensor detecting temperature by exploiting a phenomenon in which a difference between base-emitter voltages of the first and second transistors varies according to temperature,

wherein the feedback circuit comprises:

a first current mirror circuit composed of

a third transistor through an emitter of which flows an emitter current commensurate with the collector voltage of the first transistor and

a fourth transistor through an emitter of which flows an emitter current commensurate with the collector voltage of the second transistor,

the emitter current of the fourth transistor being varied so as to follow variation of the emitter current of the third transistor; and

a second current mirror circuit of which an operating voltage is determined so as to follow variation of the emitter current of the fourth transistor, the second current mirror circuit determining the emitter currents of the first and second transistors.

2. A temperature sensor comprising:

a first transistor of an npn type

of which a collector is connected via a first constant current source to a supply voltage line, and

of which a base is connected to an output terminal;

a second transistor of an npn type

of which a collector is connected via a second constant current source to the supply voltage line, and

of which a base is connected to a node between first and second resistors connected in series between the output terminal and a ground line,

the second transistor having a different emitter current density from the first transistor;

a third transistor of an npn type

of which a collector is connected to emitters of the first and second transistors, and

of which an emitter is grounded via a third resistor;

a fourth transistor of an npn type

of which a collector is connected to the supply voltage line,

of which a base is connected to the collector of the first transistor, and

of which an emitter is connected to the output terminal;

a fifth transistor of an npn type

of which a collector is connected to the supply voltage line, and

of which a base is connected to the collector of the second transistor;

a sixth transistor of a pnp type

of which an emitter is connected to the output terminal, and

of which a collector and a base are connected together;

a seventh transistor of a pnp type

of which an emitter is connected to an emitter of the fifth transistor, and

of which a base is connected to the base of the sixth transistor;

an eighth transistor of an npn type

of which a collector is connected to the collector of the sixth transistor, and

of which an emitter is grounded via a sixth resistor; and

a ninth transistor of an npn type

of which a collector is connected to a collector of the seventh transistor,

of which the collector and a base are connected together,

of which an emitter is grounded via a seventh resistor, and

of which the base is connected to bases of the third and eighth transistors.

3. A temperature sensor according to claim 2,

wherein

the sixth and seventh transistors are identical in size and characteristics,

the eighth and ninth transistors are identical in size and characteristics, and

the sixth and seventh resistors are identical in size and characteristics.

4. A temperature sensor according to claim 2, further comprising:

fourth and fifth resistors connected in series between the emitter of the fifth transistor and the ground line, the fourth and fifth resistors having resistances equal to resistances of the first and second resistors.

5. A temperature sensor according to claim 4,

wherein the resistances of the first, second, fourth, and fifth resistors can be adjusted by trimming.

6. A temperature sensor according to claim 2, further comprising:

a tenth transistor of an npn type

of which a collector is connected to the supply voltage line,

of which a base is connected to a node between the collector of the sixth transistor and the collector of the eighth transistor, and

of which an emitter is grounded via an eighth resistor.