Grid bias

Grid bias is a DC voltage applied to electron tubes (or valves in British English) with three electrodes or more, such as triodes. The control grid (usually the first grid) of these devices is used to control the electron flow from the heated cathode to the positively charged anode. Bias point in small-signal applications is set to minimize distortion and achieve sufficiently low power draw. In high-power applications, biasing is typically set for maximum available output power or voltage, with a secondary target of either low distortion or high efficiency.