Design Of A SPAD Photoelectric Detector And Readout Circuit

In recent years,the application of single photon detection,acquisition and processing technology has gradually expanded to military,industrial,agricultural,and other fields.These areas require the application of processing that converts optical signals into electrical signals.It is used in a wide range of applications in the production and economic sectors,such as precision measurement,industrial process control and medical testing.In the single photon acquisition and processing process,the optical signal is first received by the photodetector device,and then the photocurrent is received by the readout circuit and converted into a voltage signal,and finally the voltage signal is amplified and digitized.Therefore,improving the performance of the photodetector device and the readout circuit is the key to improving the sensitivity and accuracy of the photodetector.(1)This paper focuses on high-speed,weak visible and near-infrared light detectors.The working principle and indicators of photodetectors are analyzed.The performance parameters of the detector's wide spectrum,high responsivity,high speed and weak signal detection were studied.The working principle of photodetector and optoelectronic readout circuit is expounded,and the performance indexes of its device and circuit structure are designed and optimized.(2)In this paper,a high-performance photodetector device and readout circuit are designed and implemented through device and circuit structure design,simulation,layout design,layout verification and post-simulation verification.A design of an optical signal detection chip stage has been completed.Based on SMIC's 0.18?m CMOS process,a circular single photon avalanche diode(SPAD)with high edge breakdown,extended spectrum and low dark count rate was designed as a photodetector device to acquire optical signals.Secondly,based on Wanghong 0.5?m CMOS process,a weak and high-speed photoelectric analog signal readout circuit is designed.The readout circuit mainly includes a low temperature coefficient bandgap reference voltage circuit,a high linearity main operational amplifier,and a low delay comparator circuit.(3)Through the photoelectric signal test,the circular P+/deep n-well avalanche photodiode device designed in this paper can achieve more than 40% photon detection rate in the wavelength range of 490 to 775 nm under the overvoltage of 1V.In addition,the device has a good avalanche breakdown voltage and a low dark count rate of 15.14 V and 638 Hz,respectively.Through the Cadence software simulation,the overall readout circuit can achieve the reception of photocurrent of 80nA/1MHZ.The readout circuit includes a 7.85 ppm/°C low temperature drift bandgap reference circuit,a 120.6 dB common mode rejection ratio high linearity main op amp,and a 63 ns/1 MHZ comparator.And through the constant temperature and humidity platform test,the temperature coefficient of the bandgap reference voltage source circuit is 10.26ppm/°C,which verifies that the circuit has low temperature drift performance.The photoelectric signal readout chip area was 672 ?m * 780 ?m.