Issues in the readout of FIR- and millimeter-wave bolometers for astrophysical applications

Bolometers are used extensively in astrophysics for imaging and spectroscopy at wavelengths between several millimeters and 10 microns. They are particularly useful for applications requiring high sensitivity; current and planned bolometer systems are nearing the sensitivity limit imposed by background photon noise, even in the low-background conditions achieved in observatories on satellites, aircraft, and balloons. Reaching this limit will require new types of bolometers as well as improved preamplifiers to read them out. We describe two types of bolometers optimized for low-background operation and focus on the design and testing of their preamplifier circuits.