calculating resistor values for transistor biasing

CALCULATING RESISTOR VALUES FOR TRANSISTOR BIASING SERIAL

Both gain and base–emitter voltage depend on the temperature.Due to the Early effect, the current gain is affected by the collector–emitter voltage.

CALCULATING RESISTOR VALUES FOR TRANSISTOR BIASING SERIAL

The gain of a transistor can vary significantly between different batches, which results in widely different operating points for sequential units in serial production or after replacement of a transistor.The operating point of a device, also known as bias point, quiescent point, or Q-point, is the point on the output characteristics that shows the DC collector–emitter voltage ( V ce) and the collector current ( I c) with no input signal applied.Ī bias network is selected to stabilize the operating point of the transistor, by reducing the following effects of device variability, temperature, and voltage changes: By selecting the proper resistor values, stable current levels can be achieved that vary only little over temperature and with transistor properties such as β. The voltage divider configuration achieves the correct voltages by the use of resistors in certain patterns. Much more elaborate biasing arrangements are used in integrated circuits, for example, bandgap voltage references and current mirrors. In circuits made with individual devices (discrete circuits), biasing networks consisting of resistors are commonly employed. Process necessary for BJT amplifiers to work correctly A load line diagram, illustrating an operating point in the transistor's active regionīipolar transistors must be properly biased to operate correctly.

Calculating resistor values for transistor biasing