Adjustable gain CTIA cell with variable integration time for IRFPA applications

In infrared focal plane arrays (IRFPA) applications, variable gain of capacitor feedback transimpedance amplifier (CTIA) cells in readout integrated circuit (ROIC) is required to achieve a widely dynamic range and keep CTIA cells away from saturation. Selectable integration capacitors CTIA cell and a counter-based novel timing control circuit are proposed and presented in this paper. With the two features, gain of CTIA can be easily changed to accommodate the wide scene dynamic range requirements of IRFPA, as well as keep the CTIA from saturation. Moreover, the proposed circuit requires fewer devices to achieve the same maximum integration time as the conventional one does. The proposed circuit has been designed and simulated by CSMC 0.5 mum double poly triple metal (DPTM) process technology. The simulation results confirm these advantages.