On-current (Ion): definition · Chip Field Guide

Beginner

The most current a transistor passes when it is fully on. More means faster circuits.

Novice

The drain current with the gate and drain both at the supply voltage ( $V_{\mathrm{GS}} = V_{\mathrm{DS}} = V_{\mathrm{DD}}$ ), usually quoted per micrometer of width. It sets how fast a gate can charge the next one.

Expert

$I_{\mathrm{DS}}$ at $V_{\mathrm{GS}} = V_{\mathrm{DS}} = V_{\mathrm{DD}}$ , in saturation. Usually quoted in µA/µm at a stated corner and temperature. Gate delay scales roughly as $C V_{\mathrm{DD}}/I_{\mathrm{on}}$ , so $I_{\mathrm{on}}$ is the headline speed figure on a device’s I-V plot.