What Duty and Bias Mean in a Segment LCD (and Why It Changes Your Driver)

Duty: how many segments share one pin

In a static display every segment has its own connection, which gives the sharpest contrast but needs one pin per segment. To reduce pin count, segments are multiplexed: they are grouped into commons and driven one group at a time, fast enough that the eye sees a steady image. 1/4 duty means four groups, so a segment is only powered a quarter of the time.

Bias: how many voltage levels the driver uses

Multiplexing needs intermediate voltage levels to keep unselected segments from darkening. Bias describes how those levels are divided; 1/3 bias means three steps between the supply rails. More duty generally needs more bias, and the combination has to match what your controller supports.

Why it matters in practice

• Contrast: higher duty means each segment is on for a shorter time, so contrast drops if the bias is wrong.
• Ghosting: a mismatch shows up as faint segments that should be off — the classic multiplexing artefact.
• Pin count and cost: a lower duty design may need fewer pins but more glass area and a larger connector.
• Temperature: LCD fluid response changes with temperature, which is why wide-temperature designs need duty and bias chosen with the operating range in mind.

How to specify it in an inquiry

Either state the duty and bias you need, or tell us which controller you use and we will match the glass to it. If you are still choosing, tell us how many segments and icons the display must show and we will recommend the most economical combination.