Why DC biasing is necessary for transistor operation

(i) For bipolar junction transistor the point chosen to keep the transistor operating in the active mode, using a variety of circuit techniques, establishing the Q-point DC voltage and current. A small signal is then applied on top of the Q-point bias voltage, there by either modulating or switching the current, depending on the purpose of the circuit.

(ii) The quiescent point of operation is typically near the middle of DC load line. The process of obtaining certain DC collector current at a certain DC collector voltage by setting up operating point is called.

(iii) After establishing the operating point. When input signal is applied, the output signal should not move the transistor either to saturation or to cut-off. However, this unwanted shift still might occur.