A linearization technique for Cryogenic infrared readout circuit

In recent years, infrared imaging technology is more and more widely used. HgCdTe plays a crucial role in the development of infrared photodetectors due to its many advantages, and it is still the preferred material system for application. HgCdTe material (which needs to work at low temperature 110K), At low temperature, the non-ideal effect of semiconductor material has a great influence on the linearity of readout circuit. the linearity of infrared readout circuit directly affects the imaging quality. Therefore, a nonlinear correction circuit suitable for low temperature infrared readout circuit is proposed in this paper. Traditional infrared sensing circuit substrate bias effect of MOSFET (the Metal-Oxide-Semiconductor Field-Effect Transistor) make the threshold voltage with read voltage change caused the poor linearity. In this paper, a linearization technique of readout circuit is proposed, which corrects the nonlinearity introduced by the source follower in the pixel circuit on the column without changing the pixel circuit structure and the overall chip layout. In this method, the corrected output can follow the voltage change of FD node well through the negative feedback loop formed by rail-to-rail amplifier. Simulation results show that the linearity of traditional source follower is only 80% at low temperature and the error voltage is more than 300mV, while the linearity of this method can reach 99.9% after correction. The error voltage is less than 300uV. And it can solve the problem of small output swing of infrared readout circuit at low temperature. After correction, the swing can reach 1~3V, which can greatly improve the dynamic range of infrared readout circuit.