Infrared detectors are the core of infrared imaging systems, while readout integrated circuits are the key components of detectors. In order to grasp the performance of circuits quickly and accurately, a method of circuit modeling using Verilog-A language is proposed, which present a behavioral simulation model for the ROIC. At first, a typical capacitor trans-impedance amplifier(CTIA) ROIC unit is showed, then the two essential parts of it,operational amplifier and switch are modeled on behavioral level. The op amp model concludes these non-ideal factors, such as finite gain-bandwidth product, input and output offset, output resistance and so on. Non-deal factors that affect switches are considered in the switch behavioral model, such as rise and fall time, on-resistance and so on. At last time-domain modeling method for noise is presented, which is compared with the classical frequency domain method for difference. The analysis results shows that in the situation that noise interested bandwidth(NIBW) is more than 5MHz, the difference between the two methods leads to less than 1% if the sample rate of noise is larger 4 times of the NIBW
Doping concentration is the key factor affecting the performance of infrared detectors.
Based on photovoltaic HgCdTe infrared photodetectors, in order to compute the response speed in
engineering applications precisely and fastly, a theoretical estimation model is proposed. At first,
according to continuity equation of PN junctions that are radiated by infrared radiation, the mechanism
of PN junctions in a typical working situation is analyzed and an approximate solving method is
established, which shows the analytic expression of the relationship between the response speed of
photovoltaic infrared photodetectors and the doping concentration s. Then the response speed of
photovoltaic HgCdTe infrared photodetectors is compared to that of photoconductive photodetectors.
In the end, the error of the estimation model is checked, which is done through numerical analysis. The
results indicate that the response speed rises with the doping concentration increasing as the error
increases, the estimation model proposed brings the maximum error of 5.9%, if the doping
concentration is 10<sup>21 </sup>per cubic centimeter.