The effects of electrothermal feedback on the performance of a micromachine
d superconducting high T-c transition edge bolometer, over a temperature ra
nge 85-95 K, have been investigated. The system behaves nonlinearly, due to
the variation of the resistance-temperature coefficient beta with temperat
ure. Optimum operating points of constant current mode (CCM) and constant v
oltage mode (CVM) modes vary with temperature and biasing conditions. In CC
M, effective response time tau(eff) varies little with temperature. The opt
imum output signal of CVM occurs at approximately 3-5 K lower temperature w
ithin the tail region, where beta is maximum. The biasing voltage also disp
lays a maximum, above which the bolometric performance degrades. The CCM ex
hibits a comparatively limited linear dynamic range. Negative thermal feedb
ack causes a decrease of tau(eff) of up to 2 orders of magnitude in CVM. CC
M requires precise thermal stabilization at midtransition. Noise in both mo
des is limited by the 1/f contribution. Maximum D* values are slightly high
er for CVM at higher frequencies. Bolometer operation in the CVM mode requi
res cooling the heatsink below 77 K, but does not need accurate temperature
control. (C) 2000 American Institute of Physics. [S0003-6951(00)03705-0].