HD74HC138
3-to-8-line Decoder/Demultiplexer
ADE-205-444 (Z)
1st. Edition
Sep. 2000
Description
The HD74HC138 has 3 binary select inputs (A, B and C). If the device is enabled these inputs determine
which one of the eight normally high outputs will go low. Two active low and one active high enables (G1,
G2A and G2B) are provided to ease the cascading of decoders.
Features
•
•
•
•
•
High Speed Operation: tpd (A, B, C to Y) = 16.5 ns typ (CL = 50 pF)
High Output Current: Fanout of 10 LSTTL Loads
Wide Operating Voltage: VCC = 2 V to 6 V
Low Input Current: 1 µA max
Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
Function Table
Inputs
Enable
Select
Outputs
G1
G2A
G2B
C
B
A
Y0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
X
X
H
X
X
X
H
H
H
H
H
H
H
H
X
H
X
X
X
X
H
H
H
H
H
H
H
H
L
X
X
X
X
X
H
H
H
H
H
H
H
H
H
L
L
L
L
L
L
H
H
H
H
H
H
H
H
L
L
L
L
H
H
L
H
H
H
H
H
H
H
L
L
L
H
L
H
H
L
H
H
H
H
H
H
L
L
L
H
H
H
H
H
L
H
H
H
H
H
L
L
H
L
L
H
H
H
H
L
H
H
H
H
L
L
H
L
H
H
H
H
H
H
L
H
H
H
L
L
H
H
L
H
H
H
H
H
H
L
H
H
L
L
H
H
H
H
H
H
H
H
H
H
L
