The KK74ACT257 is identical in pinout to the LS/ALS257, HC/HCT257. The KK74ACT257 may be used as a level converter for interfacing TTL or NMOS outputs to High Speed CMOS inputs. This device selects a (4-bit) nibble from either the A or B inputs as determined by the Select input. The nibble is presented at the outputs in noninverted from when the Output Enable pin is at a low level. A high level on the Output Enable pin switches the outputs into the highimpedance state. TTL/NMOS Compatible Input Levels Outputs Directly Interface to CMOS, NMOS, and TTL Operating Voltage Range: 4.5 to 5.5 V Low Input Current: 1.0 A; 0.1 A @ 25C Outputs Source/Sink 24 mA