Readout circuit with dual switching mode design for infrared focal plane arrays

• The amplifier of capacitive trans-impedance amplifier can share between two pixels.
• The readout circuit reduces the complexity design of circuit for dual band sensor.
• It has lower power and area which compared to traditional CTIA.

The paper proposes a readout circuit architecture with adjustable integration time for dual-band infrared detectors. The readout circuit uses direct injection to be combined with a capacitive trans-impedance amplifier. The amplifier is sharing between two pixels to reduce the complexity of the readout circuit. The proposed device reduces power consumption and area overhead compared to traditional structures. An experimental chip was fabricated using the TSMC 0.35 μm 2P4 M 5 V process. The resulting unit pixel layout area is 40 μm × 40 μm with input photocurrent ranging from 0.11 pA to 50 nA. CTIA mode is applicable from 0.11 pA to 10 nA, while DI mode is applicable from 3.3 pA to 50 nA. The maximum operating frequency of the chip are 4 MHz. The CTIA output swing is 1.2 V, the DI output swing is 2 V. The signal to noise ratio of the readout circuit is 65 dB and power consumption is less than 9.6 mW.