DC offset cancellation circuit, differential amplification circuit with DC offset cancellation circuit, photo-electric pulse conversion circuit, pulse shaping circuit, and pulse generation circuit

A photo-electric pulse conversion circuit that converts an optical pulse signal of a generally square wave shape to at least either a non-inversion electrical pulse signal that falls at a first timing at which the optical pulse signal falls and rises at a second timing at which the optical pulse signal rises or an inversion electrical pulse signal that rises at the first timing and falls at the second timing, comprising:

• a light-current conversion circuit that converts the optical pulse signal to a corresponding current signal and outputs the current signal;
• an I-V conversion circuit that converts the current signal to a pair of corresponding differential voltage signals and outputs the differential voltage signals;
• a differential amplification circuit that amplifies the differential voltage signals and outputs a pair of differential output signals;
• and
• a pulse generation circuit that outputs at least either the non-inversion electrical pulse signal or the inversion electrical pulse signal based on the differential output signals;
• the differential amplification circuit comprising:
• a low-pass filter which performs low-pass filtration on the differential output signal inputted thereto so as to output a filtered signal;
• a hold circuit which outputs a hold filtered signal instead of the filtered signal of the low-pass filter, and which outputs the hold filtered signal corresponding to the filtered signal of the low-pass filter at the time of changing the filtered signal to the hold filtered signal;
• a mixing circuit that outputs a pair of mixed differential input signals, which are generated by mixing the filtered signal or the hold filtered signal into the differential voltage signals such that a negative feedback is performed, to the pair of differential input terminals of the differential amplification circuit;
• and
• a changeover circuit which performs changeover to a filtering state in which the differential output signals are inputted to the low-pass filter and the filtered signal is outputted to the mixing circuit at the first timing, and performs changeover to a hold state in which an input of the differential output signals to the low-pass filter are cut off and the hold filtered signal is outputted to the mixing circuit at the second timing according to the inputted non-inversion electrical pulse signal or the inversion electrical pulse signal.