The technology of digitizing analogue signals and digital signal based intelligence by integrating an analogue to digital converter(ADC)into an infrared focal plane readout circuit is currently the most advanced infrared focal plane digitizing technology in the world.As the core component of the digital readout circuit,the performance index of ADC directly affects the overall circuit performance.The system architecture of ADC can be divided into chip level ADC,Column level ADC and pixel level ADC,Column level ADC is currently the most widely used structure in the infrared focal plane.According to the requirement of ADC for column level digital read out circuit,a second order feed forward incremental Sigma Delta ADC is designed with a supply voltage of 1.8 V,an ADC conversion rate of 26 kS/s,a quantization accuracy of 14 bit,and a power consumption of less than 100 μW for a single ADC.The circuit design is carried out by CMOS process,and the simulation results show that the designed incremental Sigma Delta ADC can meet the system design specifications.