LM311
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TI single precision voltage comparator, SOIC-8. Open-collector output, strobe, offset balance, single or split supply. Datasheet-verified.
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markdownLM311
Texas Instruments · Precision voltage comparator · SOIC-8
A single high-speed precision voltage comparator in SOIC-8, more flexible than a garden-variety comparator. Its output stage brings out both the transistor collector and emitter separately, so it can switch loads referenced to any level (drive a relay, a lamp, or logic at a different voltage), and a strobe input can force the output off on command. An offset-balance pair trims input offset for precision thresholds. It runs from a single supply or split supplies and drives up to 50 V / 50 mA on the output. Use it for level detection, zero-crossing, oscillators, and interfacing analog to logic.
Pinout
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | EMIT OUT | output | Open-emitter output of the comparator's output transistor. Typically tied to VCC- (ground) or used as the low side of a level-shifted output; combined with COL OUT it forms a floating output that can drive loads referenced to either rail up to 50 V at 50 mA. |
| 2 | IN+ | input | Non-inverting comparator input. Differential input range +/-30 V (VID), single-ended input range must remain within |
| 3 | IN- | input | Inverting comparator input. Differential and common-mode limits identical to IN+; typical input offset voltage 2 mV, input offset current 6 nA at 25 C. |
| 4 | VCC- | power_in | Negative supply pin. Absolute max -18 V; recommended supply span (VCC+ - VCC-) is 3.5 V to 30 V. In single-supply operation this pin is grounded. |
| 5 | BALANCE | input | Offset-balance trim pin. Connect an external network (typically a potentiometer between BALANCE and BAL/STRB with wiper to VCC+) to null input offset voltage. May be left open when trimming is not required. |
| 6 | BAL/STRB | input | Combined balance / strobe input. When current-driven at -3 mA to -5 mA (per datasheet note: the strobe must not be shorted to ground) the output is forced into the OFF (high-impedance) state regardless of the differential input. Also serves as the second terminal of the offset-balance network. |
| 7 | COL OUT | output | Open-collector output of the comparator's output transistor. Withstands up to 50 V (VCC- + 50 V) with the emitter grounded; sinks up to 50 mA (VOL <= 1.5 V at IOL = 50 mA). Requires an external pull-up resistor for logic-level output. |
| 8 | VCC+ | power_in | Positive supply pin. Absolute max +18 V; recommended supply span (VCC+ - VCC-) is 3.5 V to 30 V. Positive-supply current ICC+ typ 5.1 mA (no load). |
Key specifications
| Parameter | Value |
|---|---|
| Type | Single precision comparator |
| Output | open-collector (separate emitter + collector) |
| Output rating | 50 V / 50 mA |
| Strobe | yes (force output off) |
| Offset trim | balance pins |
| Response time | ~200 ns |
| Supply | single 5 V or split up to ±15 V |
| Package | SOIC-8 |
Ordering variants
Same part, different packaging or reel option.
LM311D (SOIC-8, tube)LM311DR (SOIC-8, tape & reel)
CAD (KiCad official)
- Symbol:
Comparator:LM311 - Footprint:
Package_SO:SOIC-8_3.9x4.9mm_P1.27mm - 3D model: SOIC-8 (KiCad packages3D)
- 3D model files:
lm311-etched.step/lm311-etched.glbcarry the MPN laser-etched on the die in a toggleableAdom.LaserEtchgroup (Fusion-ready);lm311.step/lm311.glbare the bare package body.
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: Texas Instruments datasheet (42 pp, sha256
c4f907a0fa591db0, retrieved 2026-08-17, tier: manufacturer) - Extractor:
ds2sf(Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate. - CAD: KiCad official libraries (CC-BY-SA 4.0).