{{Short description|Addressing scheme for LCDs}} '''Passive matrix addressing''' is an addressing scheme used in early liquid crystal displays (LCDs). It is a matrix addressing scheme, meaning that only ''m'' + ''n'' control signals are required to address an ''m'' × ''n'' display. A pixel in a passive matrix must maintain its state without active driving circuitry until it can be refreshed again.

The signal is divided into a row or ''select signal'' and a column or ''video signal''. The select voltage determines the row that is being addressed and all ''n'' pixels on a row are addressed simultaneously. When pixels on a row are being addressed, a ''V<SUB>sel</SUB>'' potential is applied, and all other rows are unselected with a ''V<SUB>unsel</SUB>'' potential. The video signal or column potential is then applied with a potential for each ''m'' columns individually. An on-switched (lit) pixel corresponds to a ''V<SUB>on</SUB>'', an off-switched (unlit) corresponds to a ''V<SUB>off</SUB>'' potential.<ref>{{cite web |url=http://ethw.org/First-Hand:Liquid_Crystal_Display_Evolution_-_Swiss_Contributions#Venture:_BBC_&amp;_ROCHE|title=First-Hand Histories: Liquid Crystal Display Evolution - Swiss Contributions |work=Engineering and Technology History Wiki |publisher=ETHW |last1=Wild|first1=Peter J|accessdate=June 30, 2017}}</ref>

The potential across pixel at selected row ''i'' and column ''j'' is :<math>V_{ij} = V_\mathit{sel} - V_\mathit{on|off}</math> and :<math>V_{ij} = V_\mathit{unsel} - V_\mathit{on|off}</math> for the unselected rows.<ref>P. M. Alt, P. Pleshko ''Scanning limitations of liquid-crystal displays,'' IEEE Trans. Electron Devices, vol. ED-21, pp. 146–155, Feb. 1974.</ref>

This scheme has been expanded to define the limits of this type of addressing typical LCDs.<ref>J. Nehring, A. R. Kmetz: [https://ieeexplore.ieee.org/document/1480073 ''Ultimate limits for matrix addressing of RMS-responding liquid-crystal displays.''] IEEE Transactions on Electron Devices. Vol. 26, issue 5, pp. 795–802, May 1979.</ref><ref>T. N. Ruckmongathan, V. Arun, Babu Hemanth Kumar: [https://ieeexplore.ieee.org/document/4356461 ''Line-by-Line Addressing of RMS Responding Matrix Displays With Wavelets.''] Journal of Display Technology. Vol. 3, issue 4, pp. 413–420 December 2007.</ref>

Passive matrix addressed displays, such as ferroelectric liquid crystal displays, do not need the switch component of an active matrix display, because they have built-in bistability. Technology for electronic paper also has a form of bistability. Displays with bistable pixel elements are addressed with a passive matrix addressing scheme, whereas TFT LCD displays are addressed using active addressing.

==See also== * Active matrix addressing * Pixel geometry * Liquid crystal display

==References== <references />

{{DEFAULTSORT:Passive Matrix Addressing}} Category:Digital imaging Category:Liquid crystal displays