The KK74AC257 is identical in pinout to the LS/ALS257, HC/HCT257. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALS outputs. 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. Outputs Directly Interface to CMOS, NMOS, and TTL Operating Voltage Range: 2.0 to 6.0 V Low Input Current: 1.0 A; 0.1 A @ 25C High Noise Immunity Characteristic of CMOS Devices Output Source/Sink 24 mA