Abstract: A semiconductor apparatus comprises a semiconductor body of one conductivity type; a first impurity region of an opposite conductivity type, which is formed in the surface area of the semiconductor body; impurity regions of the opposite conductivity type, formed in the surface area of the semiconductor body, at locations away from the first impruity region; second and third impurity regions of one conductivity type, which seve as source and drain regions, respectively, and are formed in the impurity regions of an opposite conductivity type, so as to sandwich a channel reigon; and a gate electrode formed on the channel region, through an insulative layer. In this semiconductor apparatus, the impurity regions of the opposite conductivity type include fourth and fifth impurity regions, formed in the channel region such that at least parts of the fourth and fifth impurity regions overlap.

Abstract: A voltage detecting circuit includes an input circuit section including a light emitting diode and a current supplying circuit for supplying a current to this light emitting diode in response to an input voltage, and an output circuit section for generating an output voltage in response to the light emitted from the light emitting diode. This output circuit section includes a phototransistor which, together with the light emitting diode constitutes a photocoupler. A characteristic between the input voltage and the output current of the current supplying circuit represents a hysteresis characteristic.