tailieunhanh - Lecture Electrical Engineering: Lecture 19 - Dr. Nasim Zafar

The main contents of the chapter consist of the following: Base-biased (fixed bias) transistor circuits, voltage-divider-bias transistor circuits, examples and exercises. | Dr. Nasim Zafar Electronics 1 - EEE 231 Fall Semester – 2012 COMSATS Institute of Information Technology Virtual campus Islamabad Potential-Divider-Biasing Circuits: Examples and Exercises. . Lecture No: 19 Contents: Base-Biased (Fixed Bias) Transistor Circuits. Voltage-Divider-Bias transistor Circuits. Examples and Exercises. Nasim Zafar 2 References: Microelectronic Circuits: Adel S. Sedra and Kenneth C. Smith. Integrated Electronics : Jacob Millman and Christos Halkias (McGraw-Hill). Introductory Electronic Devices and Circuits Robert T. Paynter Electronic Devices : Thomas L. Floyd ( Prentice Hall ). Nasim Zafar 3 Basic Circuits of BJT: NPN Transistor Nasim Zafar 4 IE = IC + IB Transistor Output Characteristics: 5 Nasim Zafar 5 Fig 5-2a & Fig 5-4 Transistor Output Characteristics: Load Line – Biasing and Stability: Active region: BJT acts as a signal amplifier. B-E junction is forward biased and C-B junction is reverse biased. Graphical construction for determining the dc collector current IC and the collector-to-emitter voltage VCE . The requirement is to set the Q-point such that that it does not go into the saturation or cutoff regions when an a ac signal is applied. Maximum signal swing depends on the bias voltage. Nasim Zafar 6 The DC Operating Point: Biasing and Stability Active region - Amplifier: BJT acts as a Signal Amplifier. 1. B-E Junction Forward Biased VBE ≈ V for Si 2. B-C Junction Reverse Biased 3. KCL: IE = IC + IB C B E IB IE IC C B E IB IE IC 7 Nasim Zafar The DC Operating Point: Biasing and Stability Slope of the Load Line: VCC = VCE + VRC VCE = VCC - VRC VCE = VCC - IC RC 8 Nasim Zafar 9 Current Equations in a BJT: NPN Transistor Collector Current Base Current Emitter Current 9 Nasim Zafar 1. Fixed-Biased Transistor Circuits. Base-Biased (Fixed Bias) Transistor Circuit: Single Power Supply 10 Nasim Zafar 11 Base-Biased (Fixed Bias) Transistor Circuit: Advantage: Circuit simplicity. Disadvantage: Q-point | Dr. Nasim Zafar Electronics 1 - EEE 231 Fall Semester – 2012 COMSATS Institute of Information Technology Virtual campus Islamabad Potential-Divider-Biasing Circuits: Examples and Exercises. . Lecture No: 19 Contents: Base-Biased (Fixed Bias) Transistor Circuits. Voltage-Divider-Bias transistor Circuits. Examples and Exercises. Nasim Zafar 2 References: Microelectronic Circuits: Adel S. Sedra and Kenneth C. Smith. Integrated Electronics : Jacob Millman and Christos Halkias (McGraw-Hill). Introductory Electronic Devices and Circuits Robert T. Paynter Electronic Devices : Thomas L. Floyd ( Prentice Hall ). Nasim Zafar 3 Basic Circuits of BJT: NPN Transistor Nasim Zafar 4 IE = IC + IB Transistor Output Characteristics: 5 Nasim Zafar 5 Fig 5-2a & Fig 5-4 Transistor Output Characteristics: Load Line – Biasing and Stability: Active region: BJT acts as a signal amplifier. B-E junction is forward biased and C-B junction is reverse biased. Graphical construction for .