PURPOSE: To obtain a signal conversion circuit having a simple constitution, by connecting first and second negative feedback resistors between the terminals of an operation amplifier, and providing a detecting element between a voltage source and the non-inverted input terminal of the operation amplifier.

CONSTITUTION: A resistor 31 is connected between the inverted input terminal of an operation amplifier 30 and a bias terminal. A resistor 32 is connected between the inverted input terminal of the operation amplifier 30 and an output terminal. A gage resistor 33 is connected between the non-inverted input terminal of the operation amplifier 30 and a negative voltage source 36. A resistor element 34 is connected between the non-inverted input terminal of the operation amplifier 30 and a positive voltage cource 35. The resistors 31 and 32 constitute a so-called negative feedback circuit, which returns part of the output voltage of the operation amplifier 30 to the inverted input terminal.