1. Logic Levels
1) Discrete voltage represent 1 and 0
2) For example:
-0 = ground (GND) or 0 volts
-1 = $ V_{DD}$ or 5 volts
3) What about 4.99 volts? Is that a 0 or a 1?
4) What about 3.2 volts then?
5) Range of voltages for 1(5) and 0(0) 0~1V->0, 4~5V->1
6) Different ranges for inputs and outputs to allow for noise
2. What is Noise?
Anything that degrades the signal(resistance, power supply noise, coupling to neighboring wires, etc.)
ex) a gate (driver) outputs 5 V but, because of resistance in a long wire, receiver gets 4.5V
3. The Static Discipline
With logically valid inputs, every circuit element must produce logically valid outputs
Use limited ranges of voltages to represent discrete values
4. Logic Levels, Noise Margins
5. DC Transfer Characteristics(Ideal Buffer VS Real Buffer)
6. Vdd Scaling
1) In 1970's and 1980's, VDD = 5V
2) Vdd has dropped
-Avoid frying tiny transistors
-Save power
3) 3.3V, 2.5V, 1.8V, 1.5V, 1.2V, 1.0V,...
4) Be careful connecting chips with different supply voltages
🤣
5) Chips operate because they contain magic smoke
Proof: -if the magic smoke is let out, the chip stops working
7. Logic Family Examples
| Logic Family | VDD | VIL | VIH | VOL | VOH |
| TTL | 5(4.75-5.25) | 0.8 | 2.0 | 2.4 | |
| CMOS | 5(4.5-6) | 1.35 | 3.15 | 3.84 | |
| LVTTL | 3.3(3-3.6) | 0.8 | 2.0 | 2.4 | |
| LVCMOS | 3.3(3-3.6) | 0.9 | 1.8 | 2.7 |
