PENTODE

electronic vacuum tube with five electrodes. Besides the cathode, anode, and control grid of the triode (q.v.) and the added screen grid of the tetrode (q.v.), there is still another grid (suppressor grid) placed between screen grid and plate and maintained at cathode potential. Thus any electrons emitted from the plate surface by secondary emission are repelled back to the plate. The pentode can be used for almost all purposes for which vacuum tubes are used, including amplification, mixing, oscillation, and pulse generation, and in circuits for timing, control, and counting.