An input buffer having a stable trip point over at least process skew and supply voltage variations includes a first inverter stage; a second inverter stage; and an arrangement for compensating for process skew and supply voltage variations. The compensating arrangement is disposed both in the pull-up...http://www.google.com.hk/patents/US6538466?utm_source=gb-gplus-share專利 US6538466 - Buffer with stable trip point
