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Chip Power Supplies: 5V TTL and 12V CMOS (can be in range 3V-15V)

  • TTL Computer logic runs on a 5V power supply. It could run on 3.3V which would work just as well and use less current and power. But the standard remains at 5V. Just as the computer keyboard is setup like a typewriters which was designed to slow typing so the mechanical keys didn't jam!
  • CMOS Logic runs on a 12V power supply. It is used for battery backup as it uses less current and power. Having two Complementary-MOS Transistors which only use current when switching: Vcc (Voltage-collector-collector, transistor pin) -> N-type MOSFET -> Signal -> P-type MOSFET -> Gnd (Ground - 0V) instead of the TTL Transistor-Resistor setup that burns heat through the resistor constantly.
  • 12V is also used to drive computer peripherals like your Keyboard, Mouse, Disk-drive, CD-ROM and Modem. High current peripherals like monitors, speakers (but not speaker card) and printers have to have their own separate power supply but share a common Gnd (Ground - 0V) line.
  • The CMOS voltage range is 3V-15V so you can build a CMOS 40'xx series circuit on plugboard using a PP3 9V Battery. See 'Recommended Electronics Books' above and Tom Duncan's 'Adventures with... electronics / digital electronic / micro-electronics' series. Projects include a Red-Amber-Green traffic light, and 4-bit binary adder.
  • TTL 74'xx and CMOS 40'xx series chips are separate families but generally can both do the same functions: Logic Gates (NOT, NAND - the most popular on IC's, AND, OR, NOR, EX-OR, and EX-NOR - used by adder circuits), Multivibrators and Clocks, Binary Counters, 4-bit Adders, 3-to-8 Line Multiplexers, 4-bit BCD (Binary Coded Decimal) to 7-segment LED Display Decoders, Shift Registers...

  • CMOS IC Technology : Complementary Metal-Oxide Semiconductor. Developed in 1963 by Frank Wanlass at Fairchild Semiconductor. Details how Transistor-Transistor Logic works. CMOS 40'xx Series Chips are far less prone to damage from electrostatic discharge (ESD). Link from our friends at the wikipedia On-Line Encylopedia.
  • CMOS Gates Demonstation info. from Hamburg, Germany. Details how CMOS IC's are designed and fabricated.
  • TTL IC Technology : Transistor-transistor logic. Also from wikipedia. Each integrated circuit performs separate building-block functions such as:
    • Logic gates such as AND, OR, NAND, NOR, XOR, inversion
    • Flip-flops
    • Latch elements
    • Ripple, synchronous, decade, and hexadecimal counters
    • Adders
    • Shift registers
    • Timing circuits
    • Data bus drivers, buffers, tristate buffers
    • Display drivers
    • Multifunction logic
    • Level converters
    • Read-write and read-only memory
    • Programmable logic arrays

    Posted by Graham on 19 June 2006 on the EPE Chatzone: