# 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 ?
A complementary problem associated to circuit parameter estimation is the adjustment of the I-V characteristic curve as a function of ambient conditions.
Assistance characteristic curve is the control target of EPS.
Lee, "Relationship between the soil-water characteristic curve and the suction stress characteristic curve: experimental evidence from residual soils," Geotechnical and Geological Engineering, vol.
Tian, "Influence of drying-wetting cycles on soil-water characteristic curve of undisturbed granite residual soils and microstructure mechanism by nuclear magnetic resonance (NMR) spin-spin relaxation time (T2) relaxometry," Canadian Geotechnical Journal, vol.
Receiver operating characteristic curve analysis of neutrophil to lymphocyte ratio to predict lupus nephritis showed that area under the curve was 0.76.
Because, in accordance with Equation 6, the characteristic curve of the external system obeys the same quadratic relationship, the new operating point of the external system also moves from A to B.
Caption: Figure 6: Response characteristic curves of simulation verification.
After being preprocessed based on recursive least square filtering, the D-P characteristic curve of Figure 11 is shown in Figure 12, where we can see that the measurement noise and outliers are suppressed effectively.
For this approximation empirical values can be used for the unknown parameters [[rho].sub.O] and [zeta] , where [p.sub.v] is already known as a result of the characteristic curve identification in the first stage and [p.sub.Cy] is a measured signal.
Specifically, we compared FIT results with subsequent biopsy results to produce receiver operating characteristic curves for FIT and biopsy-proven neoplasias (colorectal carcinoma and colonic adenoma).
Key statement: A rubber composition having a reinforcing filler of activated carbon having a pore volume of 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.
This curve, called an item characteristic curve (ICC), is assumed to graphically depict the true relationship between the trait and the responses to the item.

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