74LS05 Hex inverter, open collector
The 74LS05 holds six inverters with open-collector outputs: the 74LS04's function, but each output only ever pulls low. It needs a pull-up resistor or a load connected to +5 V to go high, and several outputs can share one line, any one of them pulling it low.
74LS05 pinout
Top view of the 14-pin DIP package. Pin 1 is at the bottom left, beside the notch, and the numbers run anticlockwise. Power is on pin 14 (VCC, +5 V) and pin 7 (GND).
| Pin | Name | Type | What it is |
|---|---|---|---|
| 1 | 1A | Input | Input of gate 1 |
| 2 | 1Y | Output | Open collector output |
| 3 | 2A | Input | Input of gate 2 |
| 4 | 2Y | Output | Open collector output |
| 5 | 3A | Input | Input of gate 3 |
| 6 | 3Y | Output | Open collector output |
| 7 | GND | Ground | 0 V |
| 8 | 4Y | Output | Open collector output |
| 9 | 4A | Input | Input of gate 4 |
| 10 | 5Y | Output | Open collector output |
| 11 | 5A | Input | Input of gate 5 |
| 12 | 6Y | Output | Open collector output |
| 13 | 6A | Input | Input of gate 6 |
| 14 | VCC | Power | +5 V supply |
74LS05 truth table
| A | Y |
|---|---|
| 0 | 1 |
| 1 | 0 |
A 1 here means the output is off: it is pulled high only by an external pull-up resistor or load.
What the 74LS05 is used for
- Driving LEDs and common-anode display segments, sinking up to 8 mA
- Lighting extra segments alongside a 74LS47, on the same segment lines
- Wired-AND lines with one shared pull-up
The 74LS04 with open-collector outputs: each only ever pulls low, so it needs a pull-up or a load to +5 V. Two of them, or one and a 74LS47 segment output, can share a line — any one pulling low wins. Sinks 8 mA, enough for an LED or a display segment through its resistor.
Electrical summary
| Package | 14-pin DIP |
| Supply voltage | 5 V (4.75 V to 5.25 V) |
| Supply current, typical | 3.6 mA |
| Output type | Open collector — only pulls low; needs a pull-up resistor or a load to the supply |
| Output current, low | sinks up to 8 mA |
| Output current, high | none — the output does not drive high |
| 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 74HC05 and 74HCT05 use the same pin numbers, with different electrical values.
Try the 74LS05 on a breadboard
The Breadboard Simulator has the 74LS05 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.