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A screen-grid tube in which secondary emission of electrons from the anode causes the anode current to decrease as anode voltage increases, resulting in a negative resistance characteristic. Also known as negatron.
tetrodeA type of vaccum tube currently used in high-end audio amplifiers. A tetrode is like a triode with the addition of a "screen grid" between the control grid and the plate (anode). The screen grid is an electrostatic shield typically biased with a fixed voltage that isolates the control grid and protects it from voltage potential changes on the plate.
Dynatrons are special types of tetrodes that utilize a screen grid voltage higher than the plate voltage. This causes the plate current to decrease as plate voltage increases. This characteristic, known as negative resistance, is useful in oscillator circuits. See triode and diode.
|The Tetrode Uses Two Grids|
|In a tetrode, the feedback and oscillation are controlled by the addition of a screen grid between the control grid and plate.|