Low-noise readout circuit for uncooled infrared FPA

A low-noise architecture for uncooled microbolometer focal plane arrays is described. The on-chip readout circuit contains an integration circuit in which the bolometer current is directly injected into a capacitor, and exhibits extremely low noise with no decrease in signal. The simple configuration of the integration circuit makes it possible to operate more circuits in parallel, and increases the integration time and number of pixels. The bias circuit for the integration circuit is formed on the chip to reduce the effect of changes in the substrate temperature. The equivalent input noise, in which all readout noise is converted into that at the bolometer node, was 6.2 muV rms. A noise at this level is so low that can loosen the required TCR in the bolometer material. A 37-mum-pitch 320 x 240 ROIC was fabricated, and its expected NETD was 67-34 mK at a TCR of 1-2 %/K. This architecture makes it possible to produce low-cost miniature cameras.