Tunnel Diode Battery Charger

EE JULY/AUGUST 1987 After a longish absence from the semiconductor scene, the tunnel diode, also called Esaki diode, after its Japanese inven- tor, has been re-introduced thanks to the fact that it can be used to save energy. In the nineteen fifties and sixties, tun- nel diodes found many appli- cations mainly in RF circuits, where their rather special properties were exploited for making fast level detectors, oscillators, mixers, and the like. As compared with a normal diode, a tunnel type utilizes a semiconductor material with an extremely high doping level, causing the depletion layer between the p-n junction to be roughly a thousand times nar- rower than that in even the fastest of normal silicon diodes. When the tunnel diode is for- ward biased, tunnelling of the electron stream occurs across the p-n junction. Tunnelling in doped semiconductors is a phenomenon not readily ex- plainable on the basis of tra- ditional atomic theory, and can not possibly be expounded in this brie...