Detection circuit for detecting signal amplitude

A detection circuit configured to detect a peak value of an input differential signal and detect an amplitude of the input differential signal based on the peak value, comprising:

• 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 corresponding to the peak value;
• a level sensing circuit configured to sense a voltage level of the input differential signal and output a switching signal based on the voltage level;
• 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.