Presentation on theme: "Types of BJT Biasing Circuits"— Presentation transcript:
1Types of BJT Biasing Circuits ByG.KavithaECE DeptPaavai Engineering College
2Biasing Circuits of the BJT Normally, three types of circuits are used to establish dc biasing in a BJT, these are;(a) Fixed bias circuit(b) Collector-to-Base Bias Circuit(c) Voltage-Divider with Self-Bias Circuit (or) Self-Bias (or) Emitter Bias (or) Emitter-Stabilized Bias CircuitWhile designing the all four types of biasing circuits of BJT it is aimed to obtain Q-point parameters (IBQ, ICQ, VCEQ)
4The Base-Emitter Loop From Kirchhoff’s voltage law: +VCC – IBRB – VBE = 0Solving for base current:
5Collector-Emitter Loop Collector current:From Kirchhoff’s voltage law:
6SaturationWhen the transistor is operating in saturation, current through the transistor is at its maximum possible value.
7The end points of the load line are: ICsat Load Line AnalysisThe end points of the load line are:ICsatIC = VCC / RCVCE = 0 VVCEcutoffVCE = VCCIC = 0 mAThe Q-point is the operating point:where the value of RB sets the value of IBthat sets the values of VCE and IC
15Base-Emitter Loop From Kirchhoff’s voltage law: Since IE = (b + 1)IB: Solving for IB:
16Collector-Emitter Loop From Kirchhoff’s voltage law:Since IE IC:Also:
17Improved Biased Stability Stability refers to a circuit condition in which the currents and voltages will remain fairly constant over a wide range of temperatures and transistor Beta () values.Adding RE to the emitter improves the stability of a transistor.
18Saturation Level The endpoints can be determined from the load line. VCEcutoff:ICsat: