Long wavelength infrared readout circuit with background suppression function

In order to improve the sensitivity of target detection by IRFPA, the carrier generated by target radiation should be maintained as long as possible. And the proportion of thermal excitation and background radiation excitation should be reduced as much as possible. The integral capacitance of the long-wave infrared (LWIR) readout circuit (ROIC) is easily saturated under high background conditions. And the non-uniformity of the LWIR detector dark current will affect the fixed pattern noise (FPN) of the focal plane array (FPA). Based on the common mode background suppression (BDS) structure and the analysis of dark current for long-wave HgCdTe detector, the BDS circuit with non-uniformity correction was designed. Traditional background suppression circuits only used common mode background suppression or differential mode background suppression. The high-precision background memory of the differential mode background suppression module was generally within a small range. Common mode BDS and differential mode BDS were used for BDS module in this paper, which can effectively reduce the fixed graphics noise and increase the dynamic range in a larger background noise range. For this background suppression circuit, the common mode background suppression used a voltage-current conversion method, and the differential mode background suppression used a current storage type background suppression structure. The background signal was amplified during background memory and signal was reduced during BDS for differential mode BDS. It could improve BDS accuracy. The circuit adopted standard CMOS process tape out. The test result shows that the FPN of ROIC is 2.08 mV. The FPN of the FPA without background suppression is 48.25 mV. When background suppression is turned on, its FPN noise is 5.8 mV. Based on the detector's non-uniform distribution of dark current, the theoretical FPN value is calculated to be 40.9 mV. The RMS noise of the output signal of the long-wave infrared focal plane is about 0.6 mV.