| Popis: |
In our study, we designed a 512×512 readout integrated circuit (ROIC) for N-on-P short wave infrared (SWIR) detectors, which has the ability to operate with two capacitors for different input current levels from very low background applications to daytime high illumination conditions. A buffered direct injection (BDI) readout cell as input circuit provides a low input resistance, high injection efficiency, and precise biasing voltage to the photodiode at low input currents. In order to reduce the noise of the BDI readout cell, a high-performance single stage amplifier is devised, the gain of which reaches as high as 50dB. The input MOSFET of the amplifier operates at sub-threshold region to keep the photodiode at precise reverse bias and steady injection efficiency. At the same time, with the input MOSFET at sub-threshold region, the current is smaller than at saturation region, and the power dissipation is reduced to a low level. A sample and hold circuit is also part of the input unit cell architecture, which allows the infrared focal plane array (IRFPA) to be operated in full frame snapshot mode and rolling mode. To prevent the excess of total current of the ROIC, the reset time of every row has a lag of one period compared to the previous row. The simulation results confirm these advantages. With the 5.0V power supply, ROIC provides the output dynamic range over 2.5V, the well capacity more than 1×10 6 e-, and the total power dissipation less than 120mW. The final chip is fabricated with HHNEC 0.35um 1P4M process technology, and the pixel occupies a 30um×30um area. The Testing results are coincide with the simulations of the circuit. With the detecting current varies from 30pA to 1nA, the linearity of BDI is 99%, and it can be operated at the temperatures below 77K. |
