A DI ROIC With Pixel-Level Dark Current Compensation for Germanium IRFPA

This article presents the design and evaluation of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$128\times 128$ </tex-math></inline-formula> direct injection (DI) readout-integrated circuit (ROIC) for germanium-based infrared focal plane array (IRFPA). To mitigate performance degradation caused by dark current, a pixel-level compensation circuit is introduced to offset the integrated output voltage. In addition, a programmable gain amplifier (PGA) is integrated into the column channel to amplify the reduced voltage swing, thereby enhancing the dynamic range (DR). To maximize readout speed and minimize PGA power consumption, an interleaved sampling technique is implemented after the PGA, and a single-to-differential output buffer is integrated within the chip to reduce external disturbances. The ROIC achieves a large full well charge capacity of 17.5 Me- with 1.44 pF stacked MOS and MIM capacitors within a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~\mu $ </tex-math></inline-formula>m pixel pitch. The ROIC was fabricated using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18~\mu $ </tex-math></inline-formula>m CMOS process, with a chip size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.6\times 5.1$ </tex-math></inline-formula> mm2. With 3.3 V power supply, the power dissipation is only 15.88 mW. Simulation results show that the linearity of the ROIC exceeds 99.3% across different PGA gain settings. Measurement results indicate that the differential output swing reaches 2 V, the nonuniformity across the entire array is as low as 12.2 mV, the noise level is estimated at 0.71 mV, and the DR of the readout circuit is obtained as 68.99 dB.