74LS02 Quad 2-input NOR gate
The 74LS02 holds four independent 2-input NOR gates. Each output is high only when both of its inputs are low. NOR is a universal gate, like NAND. Note that its pinout differs from the other quad gates: each gate's output comes before its inputs.
74LS02 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 | 1Y | Output | Totem-pole output |
| 2 | 1A | Input | Input of gate 1 |
| 3 | 1B | Input | Input of gate 1 |
| 4 | 2Y | Output | Totem-pole output |
| 5 | 2A | Input | Input of gate 2 |
| 6 | 2B | Input | Input of gate 2 |
| 7 | GND | Ground | 0 V |
| 8 | 3A | Input | Input of gate 3 |
| 9 | 3B | Input | Input of gate 3 |
| 10 | 3Y | Output | Totem-pole output |
| 11 | 4A | Input | Input of gate 4 |
| 12 | 4B | Input | Input of gate 4 |
| 13 | 4Y | Output | Totem-pole output |
| 14 | VCC | Power | +5 V supply |
74LS02 truth table
| A | B | Y |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
What the 74LS02 is used for
- NOR-only implementations of a product of sums
- SR latches with active-high inputs
- Inverters, by tying both inputs together
Electrical summary
| Package | 14-pin DIP |
| Supply voltage | 5 V (4.75 V to 5.25 V) |
| Supply current, typical | 2.2 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 74HC02 and 74HCT02 use the same pin numbers, with different electrical values.
Try the 74LS02 on a breadboard
The Breadboard Simulator has the 74LS02 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.