1. Lecture 10 Circuit Basics of Microprocessor
Youpyo DGU

2. Unused Inputs Do not forget to connect unused inputs to High or Low.
Pull-up or Pull-down is a widely used connection.

3. Transistor Basics A digital IC basically consists of gates.
A gate consists of transistors.
Gate

4. P-transistor and N-transistor

5. Drain and Source of a Transistor

6. Connecting Multiple Outputs
(x)

7. Open Drain Terminal for MOS
If at least one input is high, output is stable low.
If two inputs are low, two transistors are off. Then the output is floating.

8. Pull-Up for Open-Drain Terminal
If at least one input is high, output is still stable low.
If two inputs are low, output is stable high.

9. Open Collector Terminal for Bipolar
output
output

10. Open Drain or Open Collector
Used to connect multiple terminals directly without using tri-state terminal or multiplexor.
Make sure to place pull-up resistors.

11. Pull-up or Pull-down Resistors
When you connect unused inputs to 0 or 1, it is recommended to use resistors between the inputs and power-supply (or Ground.)
Why? To avoid damaging the chip due to too much current flow.