Design Of Current Detection Circuit For Avalanche Photodiode

With the development of photoelectric detector and related technology,the requirement of signal detection sensitivity is improved.The laser ranging imaging system based on AvalanchePhoto Diode(APD)has the characteristics of high sensitivity,fast detection,high integration and convenience,which has been been applied in the fields of national defense,military,astronomy and so on.The interface circuit is used as the bridge between APD detector and Readout Integrated Circuit(ROIC),which can achieve optical signal detection function and define the arrival time of the photon.The dynamic response speed of the interface circuit has a direct impact on the APD detection.According to the performance of domestic InGaAs APD under different operating modes,the corresponding high performance current detection circuit is designed.It can detect weak light induced current signals and output digital logic signal,taking into account the low power consumption and compact area requirements at the same time.In Geiger mode of operation,APD is in the high gain which can generate directly continuous hundreds of a level of current signal.The current signal is converted into voltage signal by capacitive induction.Then the comparator completes the state detection and output a digital pulse signal.In view of the non-uniform problem of avalanche current caused by the deviation of APD reverse bias voltage in array applications,under the control of the relevant time sequence,the APD reverse bias excess voltage of each pixel is obtained by the precise adjustment of IN anode of the APD,and finally the uniform detection of the array APD sensitivity is achieved.In linear mode of operation,APD is in the low gain which can generate a microamp level of current signal.RGC transimpedance amplifier is used as the preamplifier,which can amplify the weak current to the level near to the Geiger mode APD and is used to compensate for the gain of the linear APD.Based on GSMC 0.18 ?m CMOS process,complete the simulation and verification of the current detection circuit for 1x4 APD array in the geiger mode.The simulation results meet the design requirements.Test results show the ciruit has the function of resetting.adjusting.detecting and quenching.The regulation range of APD reverse bias voltage is 0-1.2V and step size is 80mV.The regulation of deviation within 10mV,The overall performance meets the design requirements.Due to the parasitic effect of the chip itself and the imperfect factors introduced in the test,it makes a certain gap between the test results and the simulation results.This thesis makes a detailed analysis and puts forward some feasible suggestions for the follow-up work.