One of the key issues in the development of IR focal-plaine systems is the need for low-noise and low-power readout circuitry which is compatible with the detector technology. Superconductive circuitry offers several advantages over more conventional circuitry. These include much lower power consumption and the possibility of unique circuit topologies relevant for developing advanced monolithic detectors. On-Chip signal processing through A/D conversion with digital gamma-ray suppression and digital integration appears possible. This paper reviews the progress that TRW has made in developing several of the key components of such a superconductive read-out system. We have developed a semiconductor/ Josephson-junction 3-terminal device for direct interfacing to semiconductor detectors as well as thin-film superconductive detectors. The 3-terminal device has a current gain of ≳ 500 and provides an optimum interface to further superconductive stages. Performance when coupled to a SQUID read-out will be discussed.