A detection circuit includes a differential circuit including a pair of differential transistors configured to receive the input differential signal and a first current source, the pair of the differential transistors having a common output terminal connected to the first current source, a hold capacitor connected between the common output terminal and a reference potential for generating a hold potential, a level sensing circuit configured to sense a voltage level of the input differential signal and output a switching signal, and a switch configured to receive the switching signal and electrically connect the common output terminal and a second current source when the switching signal exceeds a threshold level being lower than the hold potential by a predetermined amount, and electrically disconnect the common output terminal and the second current source when the switching signal stays lower than the threshold level.