Patent ID: 7358776

Claim:
A signal detection circuit, the signal detection circuit being for detecting presence or absence of input of differential input signals, comprising: an amplifier section comprising: a first differential-amplifying circuit which differential-amplifies a high reference voltage signal and a low reference voltage signal to output an amplified high reference voltage signal and an amplified low reference voltage signal; and a second differential-amplifying circuit which differential-amplifies differential input signals to output differential output signals, and a comparator section provided with at least either one of a first comparator circuit including three inputs for performing simultaneous detection, that upon input of the amplified high reference voltage signal and the differential output signals, at least either one of the differential output signals is higher than the amplified high reference voltage signal, and a second comparator circuit for performing detection, that upon input of the amplified low reference voltage signal and the differential output signals, at least either one of the differential output signals is lower than the amplified low reference voltage signal.