Download Transistor Biasing and more Schemes and Mind Maps Basic Electronics in PDF only on Docsity! Transistor Biasing Transistor Biasing is the process of setting a transistors DC operating voltage or current conditions to the correct level so that any AC input signal can be amplified correctly by the transistor Transistor Biasing- S.Gayathri Priya 1 Need for Biasing A transistors steady state of operation depends a great deal on its base current, collector voltage, and collector current and therefore, if a transistor is to operate as a linear amplifier, it must be properly biased to have a suitable operating point. Establishing the correct operating point requires the proper selection of bias resistors and load resistors to provide the appropriate input current and collector voltage conditions. Transistor Biasing- S.Gayathri Priya 2 Fixed Bias The transistors base current, IB remains constant for given values of Vcc, and therefore the transistors operating point must also remain fixed.Hence referred as fixed biasing Transistor Biasing- S.Gayathri Priya 5 Fixed Bias This two resistor biasing network is used to establish the initial operating region of the transistor using a fixed current bias. This type of transistor biasing arrangement is also beta dependent biasing as the steady-state condition of operation is a function of the transistors beta β value. Transistor Biasing- S.Gayathri Priya 6 Collector to base bias This self biasing collector feedback configuration is another beta dependent biasing method that requires only two resistors to provide the necessary DC bias for the transistor. Transistor Biasing- S.Gayathri Priya 7 Dual Feedback Transistor Biasing An additional resistor to the base bias network of the previous configuration improves stability even more with respect to variations in Beta, ( β ) by increasing the current flowing through the base biasing resistors. Transistor Biasing- S.Gayathri Priya 10 Dual Feedback Transistor Biasing Transistor Biasing- S.Gayathri Priya 11 The current flowing through RB1 is generally set at a value equal to about 10% of collector current, IC. Obviously it must also be greater than the base current required for the minimum value of Beta, β. One of the advantages of this type of self biasing configuration is that the resistors provide both automatic biasing and Rƒ feedback at the same time Transistor Biasing with Emitter Feedback It uses both emitter and base-collector feedback to stabilize the collector current even more as resistors RB1 and RE as well as the base- emitter junction of the transistor are all effectively connected in series with the supply voltage, VCC. This type of transistor biasing configuration works best at relatively low power supply voltages. Transistor Biasing- S.Gayathri Priya 12
