14. Logic families and gates
CMOS transfer characteristic
Formula
Tags
Detail
The CMOS VTC inverts: low Vin yields VOH and high Vin yields VOL, threshold near VDD/2.
Explore the idea
Variables
- V
- s
- Ω
- fan-out and fan-indimensionless.
Conditions
- Logic family on a fixed supply; static levels.
Intuitive explanation
For “CMOS transfer characteristic”: VOH, VOL, VIH and VIL set noise margins and the CMOS VTC inverts between rails.
Worked example
On a CMOS VTC of , a transition centred near takes the output from nearly 5 V to nearly 0 V.
Common mistakes
- confusing VIH with VOH
- forgetting noise margin
- computing fan-out without input current
Frequently asked questions
- What must be checked before using the CMOS transfer characteristic relation?
- Use the family levels and measure margins in DC.
Also known as
- VOH VOL, noise margin, CMOS VTC, fan-out, propagation delay
Conventions
- V, s or dimensionless
Last reviewed: 2026-09-19