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

Abstract

A DC offset cancellation circuit that is capable of canceling a DC offset voltage occurring between a pair of differential output signals of a differential amplification circuit, while preventing a signal waveform from being distorted due to accumulation of AC components and a photo-electric pulse conversion circuit that is capable of generating an electrical pulse signal that accurately reproduces a rise timing and a fall timing of an optical pulse signal by canceling the DC offset voltage are provided. A photo-electric pulse conversion circuit is provided with a photodiode, an I-V conversion circuit, a first differential amplification circuit having a DC offset cancellation circuit, a second differential amplification circuit, a reference voltage generation circuit, and a comparison circuit. The DC offset cancellation circuit uses a changeover circuit to change a state of a low-pass filter with a hold function in synchronization with an inversion electrical pulse signal, and performs a negative feedback of a filtered signal which is generated by subjecting third differential signals to low-pass filtration or a hold filtered signal which is a filtered signal held during changeover.