What Is the LM339? Quad Comparator: Pinout, Open-Collector and Uses
The LM339 is an IC with four independent voltage comparators in one package. It is the quad version of the dual LM393; it compares two voltages and drives its output to a logic level. Because the outputs are open-collector, each channel needs a pull-up resistor. It is used in multi-channel threshold and window-comparator circuits; the supply is VCC pin 3, GND pin 12.
The LM339 is an IC with four independent voltage comparators in a single 14-pin package. It is the quad sibling of the dual LM393 and shares the same open-collector output and character. For the concept, see what is a comparator.
What is the LM339 used for?
When a circuit needs several threshold/comparison channels, it provides four comparators on one chip: multi-channel sensor thresholds, window comparators (is a voltage between two limits), level indicators and status monitoring. Because the output is open-collector, each channel needs a pull-up resistor.
LM339 pinout (DIP-14 / SOIC-14)
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | Output 2 | 14 | Output 3 |
| 2 | Output 1 | 13 | Output 4 |
| 3 | VCC | 12 | GND |
| 4 | Input 1− | 11 | Input 4+ |
| 5 | Input 1+ | 10 | Input 4− |
| 6 | Input 2− | 9 | Input 3+ |
| 7 | Input 2+ | 8 | Input 3− |
Note: on the LM339 the supply is VCC = pin 3, GND = pin 12 (a different layout from the quad op-amp LM324).
Key electrical specifications
| Parameter | Typical value |
|---|---|
| Number of comparators | 4 (independent) |
| Supply (single) | 2 V – 36 V |
| Supply (dual) | ±1 V – ±18 V |
| Output type | Open-collector (pull-up required) |
| Response time | ~1.3 µs |
| Input common-mode range | includes ground |
Open-collector and pull-up
Each output can only pull to ground or release (high impedance). For the high level, connect a pull-up resistor (typically 4.7–10 kΩ) between the output and VCC (or your logic voltage, e.g. 3.3 V). This is an advantage for matching different logic voltages and for wired-OR.
Limitations
- Does not work without a pull-up.
- Not a linear amplifier — use an op-amp like the LM324 for amplification.
- On noisy transitions the output can chatter unless hysteresis (a Schmitt trigger) is added.
LM339 equivalents and alternatives
- LM393: the dual (2 comparator) version.
- LM311: single, more flexible (emitter/collector + strobe) comparator.
- LM2901: the automotive (AEC-Q100) counterpart.
Find it in our catalog
To compare price and stock for the LM339 and its alternatives, use the LM339 search.