Current-voltage curves operating point

I-V curves, the formation of porous SiC was performed in the avalanche breakdown mode. For heavily (H) doped samples an operating current point of 10 mA was at the voltage of 7 V, while for moderately (M) and low (L) doped samples the operating voltage points for the same current were established at 48 and 125 V, respectively. The transient period of time during which the current approached this operating point of 10 mA was 10 s for each experiment, following which, the anodization current was constant for a period of time. 

The power of the cell, i.e. / F, is shown in Fig. 103(c) as a function of cell current. We see that this function passes through a maximum which is given by the current-voltage curve of the cell. This point of maximum power can be regarded as the best operation point, provided no other considerations dictate other values for cell voltage or current as the most suitable. 

In fact, in fuel cell modeling only two levels have been used to date ofif-design operation (based on the current-voltage curve) and dynamic models. Thus far, the design point model of the SOFC is not specific in terms of details, and often instead of any model there are merely assumed constant values of fuel cell efficiency and voltage. 

Models based on an approximation of the current-voltage curve are in fact models for off-design operation and they should be used only for specific and fixed gas compositions at both anode and cathode sides. Widespread use of the classical approach models for calculating the nominal point (called design-point) appears unjustified and, frankly, wrong. 

Figure 5.16 A schematic diagram of the current voltage curve for a Gunn diode. The device will not operate in a stable mode anywhere in the negative resistance region as marked. For the load line indicated the circuit has two stable operating points as shown.

The operating point shifts to near point 4 and beyond on the curve. It may conduct a current of 2..5-20 kA or more, during a very fast-rising voltage surge. 

After the definition of the voltage requirement (maximum and minimum voltage) the details of the polarization curve are derived. The current density and the operating point are defined at single ceU level, for example 0.7 V at 1 A/cm. ... 

Figure 3.16 shows the dependence of the current-voltage characteristics of an Hgi-xCdxTe n device designed to furnish its sensitivity maximum at 5 pm (x = 0.27) at an operating temperature of 270 K. The curves were calculated for various distances between the n junction and the point of measurement. It is readily seen that the UI characteristics are worse (necessary current density larger and dynamic resistance lower) for larger lengths. 

The operating point for a given irradiance is the current and voltage that result when we put the detector into the circuit. This current-voltage pair satisfies both the equation for the load line and for the /- V curve it is the point at which the load line and the I V curve intersect. We can generally write an equation for the load line. If we had an algebraic expression for the I V curve, we could calculate the voltage... 

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