US Patent 7447054 NBTI-resilient memory cells with NAND gates

An NBTI-resilient memory cell is made up of a ring of multiple NAND gates. The NAND gates are arranged such that one of the NAND gates has a “0” in its output, while the remaining NAND gates have a “1” in their outputs. PMOS transistors within the memory cell experience less degradation than in inverter-based memory cells. Guard-banding to account for transistor degradation may be mitigated, or the operating frequency of the memory cell may be increased.