HD74HC138
3-to-8-line Decoder/Demultiplexer
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 (G
1
,
G
2A
and G
2B
) are provided to ease the cascading of decoders.
Features
·
High Speed Operation: t
pd
(A, B, C to Y) = 16.5 ns typ (C
L
= 50 pF)
·
High Output Current: Fanout of 10 LSTTL Loads
·
Wide Operating Voltage: V
CC
= 2 V to 6 V
·
Low Input Current: 1 µA max
·
Low Quiescent Supply Current: I
CC
(static) = 4 µA max (Ta = 25°C)
Function Table
Inputs
Enable
Select
Outputs
G1
G
2A
G
2B
C
B
A
Y
0
Y
1
Y
2
Y
3
Y
4
Y
5
Y
6
Y
7
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
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