Thin-film bucket brigade device charge-transfer efficiency improvements for display applications

Aerojet's approach to improving the charge-transfer efficiency (CTE) of bucket-brigade devices (BBD) for flat panel display applications is described. The task entailed studying candidate BBD configurations, making tradeoff analyses, determining factors which affect BBD CTE efficiency and analyzing display-to-cell interface circuit considerations. Recovery from initial setback in optimizing interface circuitry between BBD and classic active matrix forced an innovative approach involving a new class of active matrix (cascode circuit) to avoid requirement for high-voltage BBDs with their attendant loss of transconductance. It is concluded that full TV format display addressing can be achieved with the 99.7% BB CTE attained. This is possible with the new matrix control architecture developed for achieving the required high yield. A program for the design, construction, assembly, and testing of flat-panel displays is recommended as a means of demonstrating the matrix control concept developed. Efforts to further improve the CTE of the BBD are also recommended.