The Design Of Infrared Detector CMOS Readout Circuit With Dark Current Suppression Exclusively

Infrared imaging detection technology has advantage of strong anti-interference ability, long detection distance, and unlimited working hours, etc. It’s widely used in military, civilian and scientific fields. In aerospace applications, the majority of the long-wave infrared radiation detectors work in high-noise background. Hg Cd Te infrared detector which are widely used has large dark current and each cell has a large dark current of non-uniformity. The output signal dynamic range is too small when using conventional readout circuit design. Some pixel signal voltages even can’t be read, which greatly reduces the dynamic range of the system.This paper designs the by-cell dark current suppression readout circuit target for this problem. Considering the variety of readout circuit input stage structures, we choose CTIA amplifier to get low noise, stable bias voltage of the two ends of the detector. We combine the design of current mirror and current memory techniques. The overall background is suppressed by the current mirror, while the current from each cell is suppressed by the memory cell. Low-power correlated double sampling structure is used to to reduce power consumption of the circuit. So the structure can be applied to the focal plane array. The circuit use CSMC 0.5um Double Poly Triple Metal Mixed Signal Process to complete the circuit flow.Circuit Simulation results show that the dark current suppression circuit structure can greatly increase the integration time. Meanwhile, the non-uniformity suppression ratio of this readout structure is up to-22.7d B, output signal swing suppression is up to-17 d B, the readout signal linearity is up to 97.6%, the smallest measure the ratio is less than-55 d B. 77 K cryogenic test results show that the CTIA input stage has excellent performance. And it can provide a stable bias voltage to the detector. Meanwhile, the N-type transistor of correlated double sampling structure can reduce the overall power consumption of the circuit effectively. By increasing the width of the current mirror ground line, the sensitivity of the current mirror to ground can be reduced, and effectively increase the linear non-uniformity of the column circuit. The design of current memory cell can effectively reduce the non-uniformity of output voltage due to dark current.The output swing can reach to 2V, the non-uniformity decrease sharply, while no increase in power consumption and circuit noise.This design achieves the desired purpose. The design of the readout circuit may be applied to photovoltaic infrared detectors whose impedance more than 106Ω. The design of wide ground line in current mirror circuit can be applied to the research of a larger scale in the future development of long column uncooled detector readout circuits. It can provide an important reference to engineering development in the long-wave infrared detector readout circuit especially.