Biasing is a term used in electronics to refer to the setting of DC operating conditions (current and voltage) of an electronic component that processes time-varying signals. It is usually used to refer to a fixed DC voltage or current applied to a terminal of an electronic component such as a diode, transistor, or vacuum tube in a circuit in which AC signals are also present, in order to establish proper operating conditions for the component. The process of obtaining an appropriate DC collector current at a certain DC collector voltage by setting up the operating point is called biasing.

In a bipolar transistor, the bias is usually specified as the direction in which DC from a battery or power supply flows between the emitter and the base. In a field-effect transistor (FET), the bias is DC voltage from a battery or power supply deliberately applied between the source and the gate. Certain bias conditions are used for specified purposes. For example, in a semiconductor P-N junction, forward bias occurs when the P-type material is positive with respect to the N-type material; in reverse bias, the P-type material is negative with respect to the N-type material. When two electrodes are at the same potential, they are said to be at zero bias.

In linear circuits involving transistors, specific DC voltages and currents are required for correct operation, which can be achieved using a biasing circuit. For example, in a transistor amplifier, a small input signal gives a larger output signal without any change in shape (low distortion): the input signal causes the output signal to vary up and down about the Q-point in a manner strictly proportional to the input. The process of obtaining an appropriate DC collector current at a certain DC collector voltage by setting up the operating point is called biasing.

In summary, biasing is the process of setting the DC operating conditions of an electronic component to establish proper operating conditions for the component in a circuit in which AC signals are also present. It is usually achieved by applying a fixed DC voltage or current to a terminal of the component. Biasing is important in linear circuits involving transistors to achieve specific DC voltages and currents for correct operation.