UNIT 4 BIASING AND STABILIZATION TRANSISTOR BIASING: To operate the transistor in the desired region, we have to apply external dec voltages of correct polarity and magnitude to the two junctions of the transistor. This is known as biasing of the transistor. Since DC voltages are used to bias the transistor, it is called as DC biasing. DC OPERATING POINT (OR) QUIESCENT POINT: Application of DC voltages (bias) establishes a fixed level of current and voltage. For transistor amplifiers the resulting DC current and voltage establish an operating point on the characteristics that define the region that will be employed for amplification of the applied signal. Since the operating point is a fixed point on the characteristics, it is called as Quiescent point (Q - Point). Note: Quiescent Still inactive and quiet. NEED FOR BIASING: To operate the transistor in the desired region. The DC sources supplies the power to the transistor circuit, to get the output signal power greater than the input signal power. LOAD LINE: It is a straight line drawn on the characteristic curve with two end points A and B. It is used to fixed the operating point of a transistor. TYPES OF LOAD LINE: DC load line AC load line
DC LOAD LINE: Consider the common emitter amplifier circuit shown.