# Characteristic Curve

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## characteristic curve

[‚kar·ik·tə′ris·tik ′kərv]
(graphic arts)
In photography, a graph that shows how increases in exposure increase the density of the film.
(mathematics)
One of a pair of conjugate curves in a surface with the property that the directions of the tangents through any point of the curve are the characteristic directions of the surface.
A curve plotted on graph paper to show the relation between two changing values.
A characteristic curve of a one-parameter family of surfaces is the limit of the curve of intersection of two neighboring surfaces of the family as those surfaces approach coincidence.

## Characteristic Curve

one of the most important indexes of a photographic material. It expresses (for specified exposure and developing conditions) the optical density obtained from photographic darkening of the material as a function of the common logarithm of the exposure that produced the darkening. (SeeSENSITOMETRY.)

## Characteristic curve

A graphical display depicting complex nonlinear relationships in electronic circuits. A typical use is to show voltage-current relationships in semiconductor devices. Device amplification capabilities, for example, are exhibited by a characteristic plot which traces output current versus output voltage with a third controlling variable as a parameter. This control variable could be the base current of a bipolar junction transistor (BJT) or the gate-to-source voltage of a metal-oxide-semiconductor (MOS) transistor.

Other characteristics often included in transistor data sheets are displays of current gain versus bias current, gain versus frequency, and input and output impedances versus frequency. Less commonly, other graphical nonlinear relationships, such as the variation of thermocouple voltage with temperature or the dependence of electrical motor torque with current, also are known as characteristic curves.

In the past, characteristic curves were used as tools in the graphical solution of nonlinear circuit equations that are followed by relationships of this type. In current practice, this analysis is performed using computer packages for circuit simulation. Designers still use characteristic curves from data sheets, however, to evaluate relative performance capabilities when selecting devices, and to provide the information needed for a preliminary pencil-and-paper circuit design. See Amplifier, Transistor

References in periodicals archive ?
Relationship between the Poultry Pressure Characteristic Curve and Its Freshness [J].
Soil characteristic curve at high suctions is affected by soil texture and is independent from soil structure.
A receiver--operating characteristic curve analysis indicated that the 20-day cut point predicted high or low future survival of postmetamorphic abalone 73.
For example, the characteristic curve on the roof has a kink as shown in Fig.
As a second example, the uncertainty analysis is applied in this section to a virtual pump flow meter, which uses the measured pump head, the pump speed, and the pump characteristic curve, to determine the flow rate through the pump.
Mayer(1967) suggested that the quality standard 'p' can be considered as a quality level, along with certain other conditions to specify an operating characteristic curve later studied by Soundararajan (1975) as the quality level corresponding to the inflection point of the OC curve.
However, to have a more comprehensive estimate of the water content over the entire range of the soil water characteristic curve, further analyses were performed.
However, this is demonstrably not the case, since the flux within the foam is governed, by stability reasons, by the peak of the liquid flux versus liquid fraction curve in Figure 4 (or, equivalently, the position at which the foam characteristic curve tangentially coincides with the operating line).
1) It could be seen that we are able to calculate a linear characteristic curve which describes a linear functional connection between the air pressure observations and the changes in height.
Analysis of data from 369 women with two prior cesarean deliveries undergoing trial of labor after cesarean (TOLAC) delivery showed the area under the receiver operating characteristic curve was 0.
15 cc/g or more, a weight average particle size of less than 140 microns, and a differential characteristic curve of pore volume versus adsorption potential by the GAED or equivalent method having a peak value at less than 5 cal/cc.
To put that in perspective, when the investigators applied the ACC/ALIA risk calculator tool to the MESA data, the area under the receiver operating characteristic curve was less impressive at 0.

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