A diode is a two- terminal electronic component that conducts current primarily in one direction (asymmetric conductance ); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes,…

A diode is a device that allows current to flow in one direction but not the other. This is achieved through a built-in electric field. Although the earliest diodes consisted of red-hot wires running through the middle of a metal cylinder which itself was located inside of a glass vacuum tube, modern diodes are semiconductor diodes.