This increased threshold voltage requires a larger gate voltage for channel inversion.

Current then flows between source and drain in a surface channel maintained by the gate voltage, which controls the concentration of mobile electrons.

Applying different back gate voltages might become a concern when designing large circuits out of these elements.

For typical gate voltages of approximately 10-15V, several watts of power may be required to drive the switch.

The effect is to increase the gate voltage necessary to establish the channel, as seen in the figure.

Next, the square root of this saturated current is plotted against the gate voltage, and the slope m is measured.

The image is interpreted as a map of the sample's sensitivity to gate voltage.

A further increase in the gate voltage eventually causes electrons to appear at the interface, in what is called an inversion layer, or channel.

This opposes its bulk counterparts, which have quadratic responses to gate voltage.

Returning to Figure 5, the gate voltage is related to the input signal by voltage division as: