Arthur S. Jensen

Current Readout Of Infrared Detectors

A buffered direct-injection (BDI) current readout for infrared detectors is described and analyzed. It is compared with the common direct-injection (DI) circuit with respect to injection efficiency, noise, and tolerance of low RoA product photovoltaic detectors. Power requirements and threshold control are also discussed. Throughout the analysis it is clear that much advantage is gained at relatively little cost by the use of a BDI structure for an integrated circuit focal plane.

Temperature limitations to infrared detectors

An attempt is made to determine an absolute lower limit on the noise of a quantum detector. A comparison is made between several types of detectors and the absolute limit curve. The equations of Kinch (1989) for XSi are used as well as those of Forrseter et al. (1989) for a superconductor.

Superconductive circuits for on-FPA IR digital signal processing

Digital signal processing (DSP) on focal plane array (FPA) is attractive for large focal planes for reducing the amount of data output to no more than that which is of interest and for simplifying the IO to a simple digital bus. However, semiconductor circuits dissipate too much power for use on the FPA, overloading the cooling system capability, and requiring too much system cooling power for many applications. On the other hand, superconductive circuits (SC) offer an attractive alternative because they dissipate only about 0.1% the power of semiconductor circuits for an equivalent circuit function. SC 12 bit A/D converter and SC shift registers demonstrated in Nb at 4 K are readily convertible to NbN at 10 K. As the development of active devices in YBa2Cu3O7 matures, these and a full complement of logic devices should be possible as high as 80 K. Scene signal and detector leakage current considerations require that long wavelength IR/FPA using quantum detectors must operate at cryogenic temperatures (< 80 K). It is no significant burden to use SC circuits at these cryogenic temperatures. SC circuits operate so much faster than semiconductor circuits and SC memory circuits are so relatively limited in size that DSP architecture has to be restructured. The derived benefit in terms of system capability will warrant this investment.