4/10/06 Transistors, Analog, and Digital Wednesday’s Reading: Section 13.1: Radio (pp. 423 – 431) Upcoming Reading Assignments: Section 13.2: Microwave Ovens (pp. 432 – 438) Section 14.1: Sunlight (pp. 445 – 453) Section 14.2: Discharge Lamps (pp. 454 – 463) Section 14.3: Lasers and LEDs (pp. 464 – 470) Section 15.1: Cameras (pp. 478 – 488) Section 15.2: Optical Recording and Communication (pp. 489 – 497) Poster Session Meetings Schedule appointment Change/Modify your topic Plan your poster Etc. Lab #9 this afternoon Bring N pole marked magnet

Capacitors Two closely spaced conducting plates Separated by a thin insulating layer Holds charge (equal and opposite, overall neutral) Potential difference between plates (charge, geometry) Applications: “Slows” things down “Stores” Charge, Potential Difference Memory Keyboards

Start with good insulator Add small impurity that “opens” up some “space” in the valence band; P(ositive)-type or p-type Add small impurity that “add” some electrons to conduction band; N(egative)-type or n-type Semi-conductors and p-n junction Taken from howstuffworks.com

Biasing the Junction

Diodes p-type semi-conductor joined to n-type semi-conductor p-n junction Results in “depletion” region Apply a potential difference across junction (like hooking up battery) “Reverse bias”  increases depletion region “Forward bias”  enough potential shrinks depletion region to nothing No depletion region means current can flow. So results in current flow in one direction! Resistors Resistance Rule (Ohm’s Law): Current proportional to voltage drop

Power Adapter

Transistors

n-channel MOSFET Metal-Oxide-Semiconductor Field Effect Transistor

Analog and Digital

Memory RAM vs. ROM Volatile vs. Non-Volatile