The VHC138 is an advanced high speed CMOS 3-to-8 decoder/demultiplexer fabricated with silicon gate CMOS technology. It achieves the high speed operation similar to equivalent Bipolar Schottky TTL while maintaining the CMOS low power dissipation. When the device is enabled, 3 binary select inputs (A0, A1and A2) determine which one of the outputs (O#0-O#7) will go LOW. When enable input E3is held LOW or either E#1or E#2is held HIGH, decoding function is inhibited and all outputs go HIGH. E3, E#1and E#2inputs are provided to ease cascade connection and for use as an address decoder for memory systems. An input protection circuit ensures that 0V to 7V can be applied to the input pins without regard to the supply voltage. This device can be used to interface 5V to 3V systems and two supply systems such as battery back up. This circuit prevents device destruction due to mismatched supply and input voltages.