Current–voltage characteristic

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Figure 1. I–V curve of a P–N junction diode (not to scale).

A current–voltage characteristic is a chart showing the relationship between the DC current through an electronic device and the DC voltage across its terminals. Electrical engineers use these charts to determine basic parameters of a device and to model its behavior in an electrical circuit. Engineers commonly refer to characteristic charts as I-V curves referring to the standard symbols for current and voltage.

Figure 1 shows an I–V curve for a P-N junction diode. Figure 2 shows a family of I–V curves for a MOSFET as a function of drain voltage with overvoltage (V_GS-V_th) as a parameter.

Figure 2. MOSFET drain current vs. drain-to-source voltage for several values of overvoltage

V G S - V t h

; the boundary between linear (Ohmic) and saturation (active) modes is indicated by the upward curving parabola

The simplest I–V characteristic involves a resistor, which according to Ohm's Law exhibits a linear relationship between the applied voltage and the resulting electrical current. However, even in this case environmental factors such as temperature or material characteristics of the resistor can produce a non-linear curve.

The transconductance and Early voltage of a transistor are examples of parameters traditionally measured with the assistance of an I–V chart, or laboratory equipment that traces the charts in real time on an oscilloscope.