Vacuum Tubes, Transistors, and ICs, Oh My!"

• Vacuum Tubes
  • Lightbulb
  • Glass tube
  • Air evacuated
  • Electricity continues to flow after element is burned off
  • Electrons flow from (ground, negative) source to (positive) sync
  • When a control grid is added
    • Negative charge on control grid -> no current from source to sync
    • Positive charge on control grid -> current from source to sync
  • This is known as a triode
  • This can then act as a switch.
  • Early tubes were at least the size of a lightbulb
  • Later were as "small as" 2 inches tall, and 1/2 inch in diameter
  • Reducing power reduces heat output, but slows things down
• Transistors
  • TRANSfer resISTOR
  • Solid state - Devices that can control current without heated elements or moving parts. (Webster's)
  • Mix silicon with neighboring elements in the periodic chart and it either becomes a source (negatively charged) or sync (positively charged)
    • Mixed with aluminum it has negative potential (P-type)
    • Mixed with arsenic it has a positive potential (N-type)
  • Apply a positive charge to N-type material and electrons will flow
  • Apply a negative charge to P-type and electrons will flow
  • Demonstrate simple PMOS and NMOS devices in tkgate, not gate as well
  • 
  • A TKGATE example
  • Transistors create much less heat, and are much smaller
  • So computers built from them can go much faster.
• ICs
  • Placing microscopic transistors on a common medium
  • Design a "map" of each layer of a circuit
  • Apply a chemical coating (containing the material) which is "set" when light is applied. (Like a photo)
  • Use the map to "set" the circuit on the medium
  • Wash away the remaining material
  • Repeat
  • Hundreds of thousands of transistors can be applied to a small chip
  • Power and space are much reduced.