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KEY TO PAGES 141-144
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SRAM:Decoder and Word-Line Decoding Circuit [10–13].
Decoder and Word-Line Decoding Circuit [10–13] Two kinds of decoders are used in SRAM: the row decoder and the column decoder. Row decoders are needed to select one row of word-lines out of a set of rows in the array. A fast decoder can be implemented by using AND/NAND and OR/NOR gates. Figure 52.7 shows the schematic diagrams of static and dynamic AND gate decoders. The static NAND-type structure is chosen due to its low power consumption, that is, only the decoded row transitions. The dynamic structure is chosen due to its speed and power improvement over conventional static NAND gates. From a low-voltage operation standpoint, a dynamic NOR-base decoding would provide lower delay times through the decoder due to the limited amount of stacking of devices. Figure 52.8 shows circuit diagrams of dynamic NOR gates. The dynamic CMOS gate as shown in Figure 52.8(a) consists of input- NMOSs whose drain nodes are precharged to a high level by a PMOS when a clock signal Φ is at a low lev...
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