Temperature detection circuit
View Patent ↗A temperature detection circuit includes, a first source follower circuit supplied with a first constant current, a second source follower circuit supplied with a second constant current, and a circuit obtaining a difference between an output voltage from the first source follower circuit and an output voltage from the second source follower circuit. Measurement errors attributable to transistor threshold voltages are canceled out by obtaining a difference between output voltages.
1. A temperature detection circuit comprising:
a first source follower circuit supplied with a first constant current;
a second source follower circuit supplied with a second constant current; and
a circuit obtaining a difference between an output voltage from the first source follower circuit and an output voltage from the second source follower circuit,
wherein a value of the second constant current is different from a value of the first constant current, and
wherein each of the first and second source follower circuits comprises a plurality of source follower circuits cascaded in multiple stages, and each of the plurality of source follower circuits cascaded in multiple stages is supplied with a constant current.
2. The temperature detection circuit according to claim 1 , wherein the first source follower circuit comprises a first source follower transistor, and a second source follower circuit comprises a second source follower transistor having a conductivity type identical to that of the first source follower transistor and a transistor size different from that of the first source follower transistor.
3. The temperature detection circuit according to claim 1 , further comprising:
a first constant current circuit supplying the first constant current to the first source follower circuit; and
a second constant current circuit supplying the second constant current to the second source follower circuit.
4. The temperature detection circuit according to claim 1 , wherein an output voltage from the circuit obtaining the difference is negative-feedback-connected as an input voltage to the first source follower circuit or as an input voltage to the second source follower circuit, so that the output voltage from the first source follower circuit and the output voltage from the second source follower circuit are brought to be equal.
5. The temperature detection circuit according to claim 1 ,
wherein the circuit obtaining the difference comprises an operational amplifier circuit having a first differential input terminal connected to a voltage output terminal of the first source follower circuit, a second differential input terminal connected to a voltage output terminal of the second source follower circuit, and an output terminal connected to a voltage input terminal of one of the first and second source follower circuits, and
wherein a voltage input terminal of the other source follower circuit is supplied with a fixed potential.
6. The temperature detection circuit according to claim 1 , wherein fixed voltages are supplied as input voltages to the first and second source follower circuits, and the circuit obtaining the difference outputs a voltage proportional to the difference between the output voltage from the first source follower circuit and the output voltage from the second source follower circuit.
7. The temperature detection circuit according to claim 1 , wherein the first and second source follower circuits and the circuit obtaining the difference are formed on an identical semiconductor substrate.
8. The temperature detection circuit according to claim 1 , wherein a source follower transistor of the first source follower circuit and a source follower transistor of the second source follower circuit are manufactured in an identical transistor manufacturing process.
9. A temperature detection circuit comprising:
a first source follower circuit comprising cascaded source follower transistors each supplied with a predetermined constant current;
a second source follower circuit comprising cascaded source follower transistors, the number of which is the same as that of the source follower transistors included in the first source follower circuit and each of which is supplied with a predetermined constant current; and
a circuit obtaining a difference between an output voltage from the first source follower circuit and an output voltage from the second source follower circuit.
10. The temperature detection circuit according to claim 9 , wherein each gate of the source follower transistors of the first and second source follower circuits, except for initial-stage source follower transistors, is connected to a source of a previous-stage source follower transistor.