74HC151 — 8-to-1 Line Data Selector / Multiplexer with Complementary Outputs

Overview

The 74HC151 (SN74HC151 / 74HCT151) is a high-speed silicon-gate CMOS 8-to-1 line data selector / multiplexer IC manufactured by Texas Instruments, Nexperia, and onsemi. Available in a 16-pin through-hole DIP-16 and surface-mount SOIC-16 / TSSOP-16 package, it routes one of eight digital data inputs ( $I_0 \dots I_7$ ) to a pair of complementary outputs ( $Y$ non-inverted, and $W$ inverted) based on a 3-bit binary address ( $S_0, S_1, S_2$ ).

Operating across a wide supply range of $2.0\text{V}$ to $6.0\text{V}$ DC with a typical propagation delay of only $15\text{ ns}$ at $5\text{V}$ , the 74HC151 features an active-LOW Strobe / Enable ( $\bar{E}$ ) input. It is widely used in digital logic design for parallel-to-serial data conversion, data bus multiplexing, digital signal routing, and universal 3-variable Boolean logic function generation (synthesizing arbitrary truth tables without discrete gate arrays).

Quick reference


Logic Family	High-Speed CMOS (74HC) / TTL-Compatible (74HCT)
Function	8-Channel to 1-Line Data Multiplexer
Package	16-pin DIP (DIP-16 / PDIP-16) / 16-pin SOIC / TSSOP-16
Supply Voltage ( $V_{CC}$ )	$2.0\text{ V}$ to $6.0\text{ V}$ (74HC) / $4.5\text{ V} \dots 5.5\text{ V}$ (74HCT)
Propagation Delay ( $t_{pd}$ )	$15\text{ ns}$ typ ( $30\text{ ns}$ max) at $V_{CC} = 5.0\text{ V}$
Output Drive Current ( $I_{OH}/I_{OL}$ )	$\pm 4.0\text{ mA}$ at $5.0\text{ V}$ ( $10\text{ LSTTL}$ load fan-out)
Outputs	Complementary True ( $Y$ ) and Inverted ( $W / \bar{Y}$ )
Enable Control	Active-LOW Enable ( $\bar{E}$ / Pin 7)

Pinout (DIP-16 Package)

text

                            ┌───┴───┐
                       I3  1│ 1   16│ VCC (+2V to +6V)
                       I2  2│       │15 I4
                       I1  3│ 74HC  │14 I5
                       I0  4│  151  │13 I6
        (True Output)  Y   5│ DIP-16│12 I7
    (Inverted Output)  W   6│       │11 S0 (Select LSB)
    (Active-Low Enable)E   7│       │10 S1 (Select)
                      GND  8│       │9  S2 (Select MSB)
                            └───────┘

Pin	Name	Type	Description
1	`I3`	Digital Input	Data Input 3
2	`I2`	Digital Input	Data Input 2
3	`I1`	Digital Input	Data Input 1
4	`I0`	Digital Input	Data Input 0
5	`Y`	Digital Output	Selected data output (Non-inverted / True)
6	`W`	Digital Output	Complementary selected data output (Inverted / $\bar{Y}$ )
7	`E`	Digital Input	Active-LOW Strobe / Enable ( $\bar{E}$ ; tie to GND to enable)
8	`GND`	Power	Common Ground reference ( $0\text{ V}$ )
9	`S2`	Digital Input	Binary Select Address Bit 2 (Most Significant Bit)
10	`S1`	Digital Input	Binary Select Address Bit 1
11	`S0`	Digital Input	Binary Select Address Bit 0 (Least Significant Bit)
12	`I7`	Digital Input	Data Input 7
13	`I6`	Digital Input	Data Input 6
14	`I5`	Digital Input	Data Input 5
15	`I4`	Digital Input	Data Input 4
16	`VCC`	Power	Positive Supply Voltage ( $+2.0\text{ V}$ to $+6.0\text{ V}$ )

Function / Truth Table

Enable ( $\bar{E}$ )	Select $S_2$ (Pin 9)	Select $S_1$ (Pin 10)	Select $S_0$ (Pin 11)	Output $Y$ (Pin 5)	Output $W$ (Pin 6)
H	X	X	X	L	H
L	L	L	L	$I_0$	$\bar{I_0}$
L	L	L	H	$I_1$	$\bar{I_1}$
L	L	H	L	$I_2$	$\bar{I_2}$
L	L	H	H	$I_3$	$\bar{I_3}$
L	H	L	L	$I_4$	$\bar{I_4}$
L	H	L	H	$I_5$	$\bar{I_5}$
L	H	H	L	$I_6$	$\bar{I_6}$
L	H	H	H	$I_7$	$\bar{I_7}$

Universal Logic Function Generation Example

The 74HC151 can implement any 3-input Boolean logic function $F(A,B,C)$ without any extra gates:

Connect inputs $A, B, C$ to select pins $S_2, S_1, S_0$ .
For each minterm of the truth table, tie the corresponding input $I_n$ to $V_{CC}$ (for logic 1) or GND (for logic 0).
The desired Boolean function output appears directly at $Y$ .

Common mistakes

Leaving Enable Pin 7 ( $\bar{E}$ ) floating: If $\bar{E}$ floats or is pulled HIGH, the multiplexer is disabled: output $Y$ is forced LOW and $W$ is forced HIGH regardless of select address inputs. Always pull Pin 7 to GND (0V) for normal operation.
Confusing with analog multiplexers (CD4051): The 74HC151 is a purely unidirectional digital logic data selector with internal CMOS logic buffers. It cannot pass bidirectional analog voltages or audio signals. (For analog signals, use the CD4051).

Notes

74HC vs 74HCT: 74HC operates from $2.0\text{V} \dots 6.0\text{V}$ with CMOS switching levels; 74HCT operates from $4.5\text{V} \dots 5.5\text{V}$ with TTL-compatible input switching thresholds ( $V_{IH} = 2.0\text{V}$ ).

Interface	8 Data Inputs (I0-I7), 3 Select Inputs (S0-S2), 1 Enable (E), 2 Outputs (Y, W)
Supply	2–6 V
Package	16-pin DIP (DIP-16 / PDIP-16) / 16-pin SOIC / 16-pin TSSOP