Current bias

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In electronics, current bias is a steady-state current that is used to partially operate a device such as a transistor, vacuum tube, solenoid, transformer or others. This is a way of bringing the device into a state where it is potentially more useful.

For example, a solenoid may then become bidirectional: a varying signal current can be imposed on a fixed bias current to modulate the total current, and make the armature controllable in two directions instead of one. In the case of a transistor or vacuum tube an analogous improvement takes place, and the device can amplify both positive and negative inputs; or the input signal may be superimposed on a better, more linear, part of the transfer characteristic.