74LS151 8-to-1 multiplexer
The 74LS151 is an 8-to-1 multiplexer. The select inputs C B A choose one of the eight data inputs D0 to D7 and pass it to the output Y, with its complement on W. The active-low strobe G′ must be low; with G′ high, Y is low and W is high.
74LS151 pinout
Top view of the 16-pin DIP package. Pin 1 is at the bottom left, beside the notch, and the numbers run anticlockwise. Power is on pin 16 (VCC, +5 V) and pin 8 (GND).
| Pin | Name | Type | What it is |
|---|---|---|---|
| 1 | D3 | Input | Input |
| 2 | D2 | Input | Input |
| 3 | D1 | Input | Input |
| 4 | D0 | Input | Input |
| 5 | Y | Output | Totem-pole output |
| 6 | W | Output | Totem-pole output |
| 7 | G′ | Input | Input, active-low |
| 8 | GND | Ground | 0 V |
| 9 | C | Input | Input |
| 10 | B | Input | Input |
| 11 | A | Input | Input |
| 12 | D7 | Input | Input |
| 13 | D6 | Input | Input |
| 14 | D5 | Input | Input |
| 15 | D4 | Input | Input |
| 16 | VCC | Power | +5 V supply |
74LS151 function table
| G′ | C | B | A | Y | W |
|---|---|---|---|---|---|
| 1 | X | X | X | 0 | 1 |
| 0 | 0 | 0 | 0 | D0 | D0′ |
| 0 | 0 | 0 | 1 | D1 | D1′ |
| 0 | 0 | 1 | 0 | D2 | D2′ |
| 0 | 0 | 1 | 1 | D3 | D3′ |
| 0 | 1 | 0 | 0 | D4 | D4′ |
| 0 | 1 | 0 | 1 | D5 | D5′ |
| 0 | 1 | 1 | 0 | D6 | D6′ |
| 0 | 1 | 1 | 1 | D7 | D7′ |
X is either value.
What the 74LS151 is used for
- Selecting one of eight signals
- Implementing any function of four variables in one package: three variables go to the selects and each data input is tied to 0, 1, the fourth variable or its complement
- Parallel to serial conversion
Any function of four variables in one package: C B A select, and each data input is tied to 0, 1, D or D′.
Electrical summary
| Package | 16-pin DIP |
| Supply voltage | 5 V (4.75 V to 5.25 V) |
| Supply current, typical | 6 mA |
| Output type | Totem-pole — drives both high and low |
| Output current, low | sinks up to 8 mA |
| Output current, high | sources up to 0.4 mA |
| Input current, low | 0.4 mA out of each input held low |
| Fan-out | one output can drive about 20 LS inputs |
Typical figures for quick reference when planning a board. Check the manufacturer's datasheet for limits and timing before committing a design. The 74HC151 and 74HCT151 use the same pin numbers, with different electrical values.
Try the 74LS151 on a breadboard
The Breadboard Simulator has the 74LS151 in its parts library: seat it on a virtual breadboard, wire it, power the board and probe the pins before you build the real thing.