74HC138D

The 74HC138D is a high speed Si-gate CMOS device and is pin compatible with low power Schottky TTL (LSTTL). The 74HC138D decoder accepts three binary weighted address inputs (A0, A1 and A3) and when enabled, provides 8 mutually exclusive active LOW outputs (Y0 to Y7). This device features three enable inputs: two active LOW (E1 and E2) and one active HIGH (E3). Every output is HIGH unless E1 and E2 are LOW and E3 is HIGH. This multiple enable function allows easy parallel expansion to a 1-of-32 (5 lines to 32 lines) decoder with just four 74HC138D ICs and one inverter. This device can be used as an eight output demultiplexer by using one of the active LOW enable inputs as the data input and the remaining enable inputs as strobes. Permanently tie unused enable inputs to their appropriate active HIGH- or LOW-state.

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