One modern tetrode transistor is a [[planar transistor|diffused planar silicon bipolar junction transistor]]<ref>United States Patent{{US patent|4143421}}, March 6, 1979. Filed September 6, 1977.</ref>, used in some [[integrated circuit]]s. This transistor, apart from the three electrodes, emitter, base and collector, has a fourth electrode or grid made of conducting material placed near the emitter-base junction from which it is insulated by a silica layer.
Another modern tetrode transistor is a [[field effect transistor]] having two gates.
