Transistors & CMOS
A tiny voltage-controlled switch. Billions of them become a computer.
A bit is a promise about voltage, not a tiny printed 0 or 1.
Electric field controls conduction.
Build a decision
| A | B | XOR |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
NAND can build any Boolean function. Combining small gates creates selectors, adders, and control.
What this model includes
Ideal Boolean logic. Electrical timing and noise are omitted.
What happens inside
Control a channel
A MOS transistor has a gate, source, and drain. The gate voltage changes conduction in the channel. Real switches have capacitance, resistance, and leakage; turning one on or off takes time and energy.
Pair complementary switches
CMOS combines n-channel and p-channel devices. In an inverter, the pull-up connects the output to the supply when the input is low; the pull-down connects it to ground when the input is high. Brief overlap and charging capacitance consume energy during transitions.
Make a reliable digital signal
Logic 0 and 1 are voltage ranges separated by noise margins. A circuit must settle before the next sampling edge. FinFET and gate-all-around are transistor geometries that improve electrostatic control; they do not change the Boolean meaning of an instruction.
P_dynamic ≈ α · C · V² · fWhat this means for your code
Low-level engineer
Learn setup/hold timing, noise margins, fan-out, and the critical path. A digital model hides analog behavior, especially around clock crossings.
Software developer
Power is not just work per second. Data movement and voltage matter; batching can let a device finish sooner and sleep longer.
Read the actual specifications
These references supply the underlying contracts and implementation details. The diagrams here are simplified teaching models.