In electronics, biasing refers to the setting of DC (direct current) operating conditions (current and voltage) of an electronic component that processes time-varying signals. Many electronic devices, such as diodes, transistors, and vacuum tubes, require a steady DC current or voltage at their terminals to operate correctly. This current or voltage is called bias, and the AC signal applied to them is superposed on this DC bias current or voltage. The operating point of a device, also known as bias point, quiescent point, or Q-point, is the DC voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied. A bias circuit is a portion of the devices circuit that supplies this steady current or voltage.

In circuits made with individual devices (discrete circuits), biasing networks consisting of resistors are commonly employed. Much more elaborate biasing arrangements are used in integrated circuits, for example, bandgap voltage references and current mirrors. A bias circuit may be composed of only resistors, or may include elements such as temperature-dependent resistors, diodes, or additional voltage sources, depending on the range of operating conditions expected. Linear circuits involving transistors typically require specific DC voltages and currents for correct operation, which can be achieved using a biasing circuit.

In summary, biasing is the process of setting the DC operating conditions of an electronic component to allow it to process time-varying signals correctly. It involves applying a steady DC current or voltage to the components terminals, which is superposed on the AC signal. Biasing circuits can be composed of resistors, temperature-dependent resistors, diodes, or additional voltage sources, depending on the range of operating conditions expected.