  We have developed two analytical models to describe the performance of
cryogenic microcalorimeters and bolometers. One of the models is suitable to
describe Transition Edge Sensor (TES) detectors with an integrated absorber,
the other is suitable for detectors with large absorbers. Both models take into
account hot-electron decoupling and absorber decoupling. The differential
equations describing these models have been solved using block diagram algebra.
Each model has produced closed form solutions for the detector's responsivity,
dynamic impedance, and noise equivalent power for phonon noise, Johnson noise,
amplifier noise, 1/f noise, and load resistor noise.
