Granted Patent B2

US 6,933,753 · App. 10/490,729 · Granted Aug 23, 2005

Abstract

Claims (21)

1. A sensor signal output circuit comprising:

a first differential amplifier including an input end connected to a first reference voltage setting part, and an other input end to which a signal is input;

a first load resistor for the first differential amplifier;

a first transistor including a gate connected to an output end of the first differential amplifier, and a source connected to a first constant current source;

a second transistor including a gate connected to a point of connection between the first constant current source and the first transistor, and a drain connected to a second constant current source;

an output terminal connected to the drain of the second transistor; and

a limiter section, the limiter section including at least:

a second differential amplifier including an input end coupled to the output terminal, and an other input end coupled to a second reference voltage setting part;

a second load resistor for the second differential amplifier; and

a third transistor including a gate connected to an output end of the second differential amplifier, and a source connected to the gate of the second transistor.

2. The sensor signal output circuit of claim 1 , wherein the limiter section further includes a limiter disengagement part.

3. The sensor signal output circuit of claim 1 , wherein the second reference voltage setting part includes a fourth transistor including a gate connected to a second reference voltage, a drain connected to a ground potential, and a source connected to the other input end of the second differential amplifier.

4. The sensor signal output circuit of claim 1 , wherein the second differential amplifier includes a sixth and seventh transistors including respective sources connected to each other, and a third constant current source connected to the sources of the sixth and seventh transistors.

5. The sensor signal output circuit of claim 4 , wherein the limiter section further includes a limiter disengagement part.

6. The sensor signal output circuit of claim 5 , wherein the limiter disengagement part includes a fifth transistor in parallel with a fourth transistor of the second reference voltage setting part, and the fifth transistor includes a drain connected to a source of the fourth transistor, a source connected to a ground potential, and a gate serving as an input end for a limiter disengagement signal.

7. The sensor signal output circuit of claim 5 , wherein the limiter disengagement part includes an eighth transistor including a source connected to the common sources of the sixth and seventh transistors of the second differential amplifier, a drain connected to a power supply potential, and a gate serving as an input end for a limiter disengagement signal.

8. The sensor signal output circuit of claim 5 , wherein the limiter disengagement part includes a ninth transistor including a source connected to the gate of the third transistor, a drain connected to a power supply potential, and a gate serving as an input end for a limiter disengagement signal.

9. The sensor signal output circuit of claim 5 , further comprising:

an abnormality detector for operating the limiter disengagement part in abnormality; and

an output saturation part for holding an output voltage at a voltage lower than a second reference voltage upon receipt of an abnormality detection signal output from the abnormality detector.

10. The sensor signal output circuit of claim 9 , wherein the output saturation part includes a tenth transistor including a drain connected to the input end of the first differential amplifier that is provided with a first reference voltage, a source connected to a ground potential, and a gate connected to the abnormality detector.

Assignments (7)