DIRECT DRIVE ZERO Vt-FEEDBACK LSSD SRL WITH DUAL SECOND STAGE FEEDBACK
Original Publication Date: 1985-Aug-01
Included in the Prior Art Database: 2005-Feb-19
An improved level sensitive scan design (LSSD) shift register latch (SRL) is described, incorporating dual feedback and direct-drive in the second (L2) latching stage. Direct drive is used for L1 stage pullup devices 7 and 9, and all L2 stage pullup devices shown in the figure, resulting in the pullup current adjusted as needed, versus the standard depletion load current source. Zero threshold voltage (Vt) devices are used both for feedback and as supplementary pullup devices 9, 11, 16, 22 and 24. As feedback, their resistance is greater--limiting current spikes more effectively than depletion mode devices. As supplementary pullup devices, they allow reduction in the size of the depletion devices 7, 12, 18, 20 and 25 and hence DC power reduction, without sacrificing performance.