Valentine's Day, 2000
Gates revisted
Properties of gates
Logic levels
- Positive logic
- Negative logic
Noise margins
This is just an example
- Value ranges for output
- Low is 0.0V to 0.4V
- High is 2.4V to 5.0V
- Input ranges to achieve those output ranges
- Low can be 0.0V to 0.8V
- High can be 2.0V to 5.0V
- Noise margins
- Low margin is 0.4V to 0.8V
- High margin is 2.0V to 2.4V
Fan out
Number of input gates that can be driven be an output while maintaining
voltage levels.
- Current sink
- Current that can be driven low (100 µA)
- Current source
- Current that can be driven high (10 µA)
Power dissipation
- Power generates heat. Heat destroys chips.
- Power drains batteries. Cell phone doesn't work!.
Propagation delay
How long does it take a gate to do its job?
MOS
- MOS
- metal-oxide-semiconductor
- CMOS
- complementary MOS
- FET
- field-effect transistor
CMOS offers low power, high fan-out, good integration.
Integrated circuits