tailieunhanh - Lecture Electrical Engineering: Lecture 21 - Dr. Nasim Zafar

The main contents of the chapter consist of the following: Common-emitter characteristics, BJT as an amplifier, small signal operation, BJT amplifiers using coupling and bypass capacitors, BJT amplifiers-DC equivalent circuits. | Dr. Nasim Zafar Electronics 1 - EEE 231 Fall Semester – 2012 COMSATS Institute of Information Technology Virtual campus Islamabad BJT as an Amplifier. Small-Signal Operation and Equivalent Circuits: Lecture No. 21 Contents: Common-Emitter Characteristics. BJT as an Amplifier. Small Signal Operation. BJT Amplifiers using Coupling and Bypass Capacitors. BJT Amplifiers-DC Equivalent Circuits. 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 Lecture No. 21 Reference: Microelectronic Circuits: Adel S. Sedra and Kenneth C. Smith. Nasim Zafar 4 Introduction Common-Emitter Characteristics-I: We had discussed Common Emitter Current-Voltage characteristic curves extensively to understand: How the transistor operates as a linear signal amplifier for the ac signals. The basis for the amplifier application is the fact that when the BJT is operated in the active-mode, it acts as the voltage-controlled-current source: Changes in the base-emitter voltage VBE give rise to changes in the collector current Ic. Thus, in the active-mode, the BJT can be used to implement a transconductance amplifier. Nasim Zafar 5 Introduction Common-Emitter Characteristics-II: Once these basics are understood we will understand: How we can replace the transistor by a small ac-signal equivalent circuit. How to derive a simple ac equivalent circuit from the characteristic curves. Some of the limitations of our simple equivalent circuit. 6 Nasim Zafar The Common-Emitter Amplifier Circuit: Nasim Zafar 7 Common-Emitter Amplifier Circuit: The common-emitter amplifier exhibits high voltage and current gain. The output signal is 180º out of phase with the input. 8 Nasim Zafar 8 Fig. 6-8 ce amp Point A corresponds to the positive peak. Point B corresponds to the | Dr. Nasim Zafar Electronics 1 - EEE 231 Fall Semester – 2012 COMSATS Institute of Information Technology Virtual campus Islamabad BJT as an Amplifier. Small-Signal Operation and Equivalent Circuits: Lecture No. 21 Contents: Common-Emitter Characteristics. BJT as an Amplifier. Small Signal Operation. BJT Amplifiers using Coupling and Bypass Capacitors. BJT Amplifiers-DC Equivalent Circuits. 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 Lecture No. 21 Reference: Microelectronic Circuits: Adel S. Sedra and Kenneth C. Smith. Nasim Zafar 4 Introduction Common-Emitter Characteristics-I: We had discussed Common Emitter Current-Voltage characteristic curves extensively to understand: How the transistor operates as a linear signal amplifier