TAILIEUCHUNG - Lecture Electrical Engineering: Lecture 20 - Dr. Nasim Zafar

The main contents of the chapter consist of the following: Most transistors amplifiers are designed to operate in the linear region; the common-emitter amplifier has high voltage and current gain; the common-collector has a high current gain and voltage gain of 1. it has a high input impedance and low output impedance. | Dr. Nasim Zafar Electronics 1 - EEE 231 Fall Semester – 2012 COMSATS Institute of Information Technology Virtual campus Islamabad Transistor as an Amplifier Circuit: . Lecture No: 20 Contents: Introduction. Amplifier Gain. Common Emitter Amplifier. Nasim Zafar 2 Amplifier Gain: Nasim Zafar 3 Amplifiers are 2-port networks: input port output port A is called the amplifier gain. If the gain is constant, we call this a linear amplifier. Transistor Specifications: Maximum collector current, IC . Maximum power dissipated, PD PD = IC * VCE Nasim Zafar 4 Transistor Specifications: Minimum C-E voltage for breakdown, V(BR)CEO Carefully examine absolute max ratings. DC current gain variable β = hFE in specs. Nasim Zafar 5 Amplifier Gain in Decibels: Nasim Zafar Amplifier gain is expressed in decibels (dB) Originally it was expressed as “Bels” (named after Alexander Graham Bell), but these proved to be of insufficient size so we multiply “Bels” by 10 “decibels.” Decibels are a log-based ratio and are therefore dimensionless. Purpose: We want to measure the ratio of some value relative to another (. sound power in a stereo amplifier). Derivation of dB (Cont.) 6 6 Derivation of Decibels (Contd.): Nasim Zafar Ratio of power of interest (call it “p1”) to some other reference power (say, p2): However, these values are generally quite huge and tend to be logarithmically related; thus, creation of “the Bel:” 7 7 Derivation of Decibels (Contd.): Nasim Zafar However, the Bel is a bit too small, so let’s multiply it by 10 and call it a decibel (10 x Bel = 1 dB). Which gives us the decibel expression for power: 8 8 Exercise: dB for Voltage: Nasim Zafar 9 First, let’s relate voltage to power: Exercise: dB for Voltage: Nasim Zafar 10 Upon substitution: Which gives us the decibel expression for voltage: Some Physical Conclusions: Nasim Zafar If dB is positive, then v1 > v2, the signal is amplified. If dB is negative, then v1 < v2, the signal is attenuated. If dB is 0, then .

• Điện - Điện tử
• Electrical engineering
• Electronic devices
• Lecture Electrical Engineering
• Semiconductor materials
• Amplifier gain
• Common emitter amplifier
• electrical
• electronic and electrical industry
• electrical professional
• specialized dictionaries li arts
• Electrical Engineering Dictionary
• The electrical engineering handbook
• The electrical engineering
• The hall effect
• Power systems
• Electrical machines
• Digital devices
• Computer engineering
• Electrical Engineering Dictionar
• Summary of mechanical engineering and engineering mechanics doctoral thesis
• The mechanical model and calculating design
• Electrical generator for sea wave energy
• The electrical generator
• Vietnams sea condition
• Passive components
• Voltage and current sources
• Linear circuit analysis
• Passive signal processing
• Microelectronic circuits
• Integrated electronics
• Biasing stability
• Fixed bias circuits
• Common emitter characteristics
• Small signal operation
• BJT amplifier circuits
• Discrete circuit design
• Transistor amplifier
• DC Analysis
• Characteristic parameters
• BJT internal capacitances
• High frequency BJT model
• Qualitative operation of MOSFET
• Channel for current flow
• MOS field effect transistors
• Current voltage characteristics
• Circuit symbol
• MOSFET Circuit
• Voltage biasing scheme
• Fixing voltage
• Semiconductor devices
• Carrier transport in semiconductors
• Bipolar Junction Transistors