Current measurement Shape measurement Avalanche photodiodes Detectors CMOS process Noise measurement Leakage currents application specific integrated circuits avalanche photodiodes CMOS integrated circuits leakage currents mixed analogue-digital integrated circuits nuclear electronics particle calorimetry readout electronics electromagnetic calorimeter super tau-charm factory front-end readout ASIC avalanche photodiode detectors readout circuits mixed-signal CMOS process signal-to-noise ratio DC-coupled APD readout ASIC photomultiplier avalanche integrated circuit readout calorimeter electromagnetic noise low electronics semiconductor detector particle source nucleus nonlinear