Electronic Circuits 1 - Lecture Notes

Introduction

• Instructor: Behzod Razavi
• Course Objective: Build the foundation for analysis and design of electronic circuits.

Basic Circuit Theory Review

• Learned Concepts: KVL, KCL, Norton equivalent, Thevenin equivalent, resistors, capacitors, inductors, transformers.
• Basic Components: Only two-terminal devices, limited applications.

Electronic Components

• Added Components: Diodes, transistors (bipolar and MOS), operational amplifiers (op amps).
• Importance: Allows for building more complex and sophisticated circuits.

Semiconductor Physics

• Need for Understanding: Understanding device operation is crucial for circuit design.
• Course Focus: Basic semiconductor physics to understand device operation.

Course Outline

1. Semiconductor Physics: Basic level foundation on semiconductors.
2. Devices
   • Diodes: Inner workings and modeling (Ohm's law for resistors, current-voltage relationship for diodes).
   • Transistors: Bipolar and MOS transistors, their operation, modeling, and circuit design.
   • Operational Amplifiers: Understanding and using op amps in circuits.
3. Application Examples: Practical applications in daily life (e.g., cell phone transmitter and receiver circuits).
4. Special Series - Frontiers in Electronics: Examples of electronics applications in real life to appreciate the subject's relevance.

Semiconductor Physics Details

• Atoms and Electrons: Nucleus and electrons in orbitals. Valence electrons (outer shell) are crucial for interactions.
• Silicon Atom: 4 valence electrons, forms a crystal lattice by sharing electrons with neighboring atoms.
• Conductivity: Pure silicon has a certain level of free electrons at finite temperatures allowing it to conduct electricity.
• Density of Electrons: Function of temperature, follows an exponential relationship based on the bandgap energy (E_g).
• Important Constants: Boltzmann's constant (k ≈ 1.38 x 10^-23 J/K).

Charge Carriers

• Types
  1. Electrons: Free electrons that move and conduct current.
  2. Holes: Positive charge carriers created by the absence of an electron in a bond.
• Movement of Charge Carriers: Electrons and holes can both move, creating currents.
  • Hole Movement: Slower due to release and trap processes.
• Carrier Density in Pure Silicon: Equal density of electrons and holes, given by n_i (intrinsic carrier density).

Modifying Carrier Densities

• Doping: Introducing impurities to increase the number of free charge carriers.
  • Donor Atoms: Example - Phosphorus (adds free electrons), leads to n-type silicon.
  • Acceptor Atoms: Example - Boron (creates holes), leads to p-type silicon.
• Doping Levels: Lightly doped (10^15 atoms/cm³) vs. heavily doped (10^17 atoms/cm³).
• Resulting Carrier Densities: Higher free electron or hole densities due to the doped impurities.

Key Equations

• Intrinsic Carrier Density (nᵢ): Given by empirical data, relates to temperature and bandgap energy.
• Carrier Density Product Rule: N x P = nᵢ² for a doped semiconductor.

Practical Example

• Cell Phone Transmitter and Receiver
  • Transmitter Components: Microphone, amplifier, modulator, power amplifier, oscillator, antenna.
  • Receiver Components: Antenna, low noise amplifier, processing circuitry, speaker.
  • Operation Principle: Wireless transmission and reception of voice/data signals using modulated high-frequency carriers.

Conclusion

• Next Steps: Dive deeper into semiconductor physics, understand charge carriers, and begin exploring semiconductor devices like diodes, transistors, and op amps in more detail.