Comparison of noise and signal

It is evidently insufficient to consider only the response of a detector when analysing its usefulness for a particular application. It is generally necessary to analyse both intrinsic and extrinsic noise signals and compare them with the response. The result of this comparison can be expressed in many different ways. One of the most useful is the noise-equivalent power nep which is the power of an rms signal input (in watts) required to give a response equal to the total rms noise voltage AVN. Then  

The nep is usually expressed in units of WHz-1/2 (being specified for a particular frequency and unit bandwidth), or occasionally in W (being the ratio of broadband noise to responsiv-ity at a specified frequency). A figure-of-merit frequently used in the discussion of detector performance is the specific detectivity D, which is defined as  

to maximize D in the region where Johnson noise dominates, it is desirable to maximize  

11 Pyroelectric Ceramics and Thin Films Characterization, Properties and Selection 

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