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Liquid Crystal Display Driver Circuit and Polysilicon Components Therefor

IP.com Disclosure Number: IPCOM000051451D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Depp, SW: AUTHOR [+2]

Abstract

This driver circuit Permits relatively large alternating potential to b applied across a liquid crystal display (LCD) cell, while limiting the average direct potential to a non-degrading value due to a polysilicon transistor, which has a relatively high threshold, and a polysilicon load resistor, which has a relatively high intrinsic resistivity. The transistor and the resistor are laid down in a simplified semiconductor device fabrication process.

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Liquid Crystal Display Driver Circuit and Polysilicon Components Therefor

This driver circuit Permits relatively large alternating potential to b applied across a liquid crystal display (LCD) cell, while limiting the average direct potential to a non-degrading value due to a polysilicon transistor, which has a relatively high threshold, and a polysilicon load resistor, which has a relatively high intrinsic resistivity. The transistor and the resistor are laid down in a simplified semiconductor device fabrication process.

The driver circuit 10 is but one of a number (equal, for example, to the product of the numbers of row and of column conductors) of such circuits for an X-Y matrix. A selecting field-effect transistor (FET) 12 has a gate electrode connected to a column conductor 14 of a matrix. The drain electrode is connected to a row conductor 16 which has direct potential applied thereto, and the source electrode is connected to a capacitor 18 and the gate electrode of a driver transistor 20. The former is arranged for storing selection-holding potential, and the latter is arranged for quenching an LCD cell 22 by presenting a substantially short circuit there-across.

In operation, a relatively high value of alternating potential is applied at a terminal 24 across a series circuit comprising a resistor 26, made of polysilicon, and the cell 22 for exciting the cell. The driving transistor 20 is held off for activating the cell and turned on for effectively shorting the cell 22 to deactivate it. The driving transistor must be blocked for the alternating potential to be as high as desired...