Biasing in
electronics is the method of establishing predetermined
voltages or
currents at various points of an
electronic circuit for the purpose of establishing proper operating conditions in
electronic components. Many electronic devices such as
transistors and
vacuum tubes, whose function is
processing time-varying (
AC)
signals also require a steady (DC) current or voltage to operate correctly — a
bias. 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 steady-state voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied.