Part of the Day · LM393 — SOIC-8 dual voltage comparator

Part of the Day · 2026-10-26

The most common part with two comparators that compare two voltages and report which one is higher as an on/off signal. The output is open-collector, so with a pull-up resistor you can match it to the logic voltage you need.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOIC-8 · top view · approx. 15×)

Pins 1 1OUT (comparator 1 output) · 2 1IN− (comparator 1 inverting input) · 3 1IN+ (comparator 1 non-inverting input) · 4 GND (ground) · 5 2IN+ (comparator 2 non-inverting input) · 6 2IN− (comparator 2 inverting input) · 7 2OUT (comparator 2 output) · 8 VCC (supply)

Package SOIC-8

Key specifications

Values are from the Texas Instruments datasheet.

Marking and pins

Typical uses

• Voltage monitoring — battery undervoltage / overvoltage detection
• Turning sensor signals into on/off signals (temperature, light, level switches)
• Zero-crossing detection, simple oscillator and PWM circuits
• Logic level shifting to a different voltage (open-collector output + pull-up)

Companion & similar parts

• LM393B — Newer version from the same datasheet — 2 ~ 36V, offset max 2.5mV, 1µs response, drop-in replacement
• LM2903 — Same pinout, -40 ~ 125℃ temperature range (automotive / industrial)
• LM339 — Quad comparator of the same family (14 pins)
• LM358 — Op amp with the same pinout — but a comparator has a different output type, so they are not interchangeable

Because the output is open-collector, it cannot go high without a pull-up resistor (the datasheet test condition uses a 5.1kΩ pull-up). On the other hand, you can pull up to a voltage different from VCC (e.g. 3.3V logic), and several outputs can be tied together for an AND function. If an input goes more than 0.3V below GND, the output can be incorrect.