We present a theoretical analysis and experimental evaluation of a tra
nsition-edge superconducting bolometer for detecting infrared and mill
imeter waves. The superconducting film is voltage biased and the curre
nt is read by a superconducting quantum interference device ammeter. S
trong electrothermal feedback maintains the sensor temperature within
the transition, gives a current responsivity that is simply the invers
e of the bias voltage, and reduces the response time by several orders
of magnitude below the intrinsic time constant C/G. We evaluated a vo
ltage-biased bolometer that operates on the T-c similar to 95 mK trans
ition of a tungsten film with a thermal conductance of G similar to 1.
2 x 10(-9) W/K. As expected, the electrical noise equivalent power of
3.3 x 10(-17)/W root Hz is close to the thermal fluctuation noise limi
t and is lower than that of other technologies for these values of G a
nd temperature. The measured time constant of 10 mu s is similar to 10
0 times faster than the intrinsic time constant. (C) 1996 American Ins
titute of Physics.