Abstract:Longwavelength infrared focal plane arrays, which have large dark currents, usually work under high backgrounds. The photo current is much smaller than background current. Therefore the integration capacitor is easily saturated. All of these lead to a poor SNR (signal noise ratio). Longer integration time, better contrast and dynamic range can be achieved effectively by adding a current suppression structure. In this paper, several typical background suppression techniques and how they work were introduced. According to the advantages and disadvantages of each structure compared through simulation, different fields of application for which these background suppression methods were suitable had been pointed out in the use of infrared focal arrays readout circuits.