The optimal signal to noise ratio for detectors based on superconducti
ng tunnel junctions (STJ) is compared for the cases of a detector cons
isting of one single STJ, as well as of series and of parallel connect
ions of STJs. A single STJ exhibits the best signal to noise ratio if
the signal charge is independent of detector area. If signal charge in
creases in proprotion to the detector area, a parallel or a series con
nection of STJs would provide the optimum signal to noise ratio. The s
ignal to noise ratio is deduced as function of junction parameters.