Germanium photoconductors are currently the most sensitive detectors for use in low background, far infrared applications. In particular, between the wavelengths of 40 micrometers and 200 micrometers , these detectors have been used in a number of existing or planned systems for space infrared astronomy. We describe briefly the physical mechanisms of photoconductivity, including a discussion of various non-ideal behaviors seen at low backgrounds. The requirements for specialized cryogenic electronics are discussed along with some current implementations. Examples of past focal plane array designs are given, and the extension of the technology to large format imaging arrays is described.