Analysis and Design of Analog Front-~end Circuitry for Avalanche Photodiodes (APD) and Silicon Photo-~multipliers (SiPM) in Time-~of-~flight Applications
This thesis reports the analysis and design of analog front-end circuitry for reading out signals from avalanche photodiodes (APD) or silicon photomultiplier (SiPM) in time-of-flight (ToF) applications. An integrated circuit was designed using AMS SiGe 0.35 um BiCMOS process. The chip measured 2 mm x 2 mm (2000 umx2000 um). The chip mainly contains the following circuits: an APD with photoactive area measuring 24 umx24 um, an SiPM with 8x8 APDs with 236 k ohm quench resistors, a transimpedance amplifier (TIA), a comparator and a R-2R digital to analog converter (DAC). The TIA is based on the shunt-shunt feedback topology. The TIA gain can be digitally set using two input bits to range from -0.9 k ohm to -14.44 k ohm with a bandwidth ranging from 93 MHz to 113 MHz. Photodetector capacitance on TIA input reduces the bandwidth. The maximum positive input current dynamic range of the TIA is 294 uA. The TIA consumes a power of 7.1 mW. The comparator has a maximum speed of 265 MHz with input sensitivity down to 50 uV and consumes about 6.6 mW of power. The R-2R DAC has a 10-bit resolution with maximum differential nonlinearity (DNL) and integral nonlinearity (INL) of -0.14 LSB and -0.09 LSB respectively with no load. Design considerations for all the blocks are given and simulation results are compared to hand calculations. The TIA, comparator and DAC are connected as a system and the simulation is functional. Using this system to implement a time-of-flight LiDAR (light detection and ranging), a range resolution down to 1.2 m (3.9 ft) can be achieved with photodetector capacitance of 0.1 pF.