A technique of operating a device comprising a patterned conductor layer defining source electrode circuitry and drain electrode circuitry for a plurality of transistors; a semiconductor layer providing a respective semiconductor channel for each transistor between source electrode circuitry and drain electrode circuitry; and gate electrode circuitry overlapping the semiconductor channels of the plurality of transistor devices for switching the semiconductor channels between two or more levels of conductance; wherein the technique comprises using one or more further conductors independent of said gate electrode circuitry to capacitatively induce a reduction in conductivity of said one or more areas of said semiconductor layer outside of said semiconductor channels.