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The threshold voltage, commonly abbreviated as V th or V GS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (V GS) that is needed to create a conducting path between the source and drain terminals. It is an important scaling factor to maintain power efficiency.
However, in most fielded systems, unwanted clutter and interference sources mean that the noise level changes both spatially and temporally. In this case, a changing threshold can be used, where the threshold level is raised and lowered to maintain a constant probability of false alarm. This is known as constant false alarm rate (CFAR) detection.
The JND formula has an objective interpretation (implied at the start of this entry) as the disparity between levels of the presented stimulus that is detected on 50% of occasions by a particular observed response, [3] rather than what is subjectively "noticed" or as a difference in magnitudes of consciously experienced 'sensations'.
In the above formula, P is measured in units of power, such as watts (W) or milliwatts (mW), and the signal-to-noise ratio is a pure number. However, when the signal and noise are measured in volts (V) or amperes (A), which are measures of amplitude, [note 1] they must first be squared to obtain a quantity proportional to power, as shown below:
A classification model (classifier or diagnosis [7]) is a mapping of instances between certain classes/groups.Because the classifier or diagnosis result can be an arbitrary real value (continuous output), the classifier boundary between classes must be determined by a threshold value (for instance, to determine whether a person has hypertension based on a blood pressure measure).
where is the threshold of decision, set to 0 when = =. We can use the average energy of the signal E = A 2 T {\displaystyle E=A^{2}T} to find the final expression : p e = 0.5 erfc ( E N o ) . {\displaystyle p_{e}=0.5\,\operatorname {erfc} \left({\sqrt {\frac {E}{N_{o}}}}\right).} ±§
The above formula only detects changes in the positive direction. When negative changes need to be found as well, the min operation should be used instead of the max operation, and this time a change has been found when the value of S is below the (negative) value of the threshold value.
The false positive rate (false alarm rate) is = + [1]. where is the number of false positives, is the number of true negatives and = + is the total number of ground truth negatives.