Current–voltage characteristic

Electronic engineers use these charts to determine basic parameters of a device and to model its behavior in an electrical circuit.

This is usually displayed on a more complex current–voltage graph with multiple curves, each one representing the current–voltage relationship at a different value of current or voltage on the third terminal.

[1] For example the diagram at right shows a family of I–V curves for a MOSFET as a function of drain voltage with overvoltage (VGS − Vth) as a parameter.

The transconductance and Early voltage of a transistor are examples of parameters traditionally measured from the device's I–V curve.

The figure to the right shows an I–V curve that is more relevant to the currents in excitable biological membranes (such as a neuronal axon).

The current–voltage characteristics of four devices: a resistor with large resistance , a resistor with small resistance, a P–N junction diode , and a battery with nonzero internal resistance. The horizontal axis represents the voltage drop , the vertical axis the current . All four plots use the passive sign convention .
MOSFET drain current vs. drain-to-source voltage for several values of the overdrive voltage , ; the boundary between linear ( ohmic ) and saturation ( active ) modes is indicated by the upward curving parabola.
The quadrants of the I–V plane. Power sources have curves passing through the red regions.
An approximation of the potassium and sodium ion components of a so-called "whole cell" I–V curve of a neuron.