LM393

The LM393 is TI's dual voltage comparator, containing two independent precision comparators in an 8-pin package with low input offset voltage (2 mV max on standard grade, 1 mV on LM393B), open-collector outputs, and the ability to operate from a single 2 V to 36 V supply or dual ±1 V to ±18 V supplies. Unlike op-amps, comparators are optimized for large-signal switching — they have no internal frequency compensation, propagate inputs to output in under 1.3 µs, and tolerate large differential input voltages without latch-up.

The open-collector output is the key feature: it can sink up to 20 mA and be pulled up to any voltage between 0 V and 36 V, independent of the comparator's own supply. This makes level translation trivial — run the LM393 at 5 V, pull the output up to 3.3 V, and you have a clean 3.3 V logic signal. Multiple outputs can also be wire-OR'd together for multi-threshold detection.

The input common-mode range includes ground, which is why the LM393 dominates low-side current-sensing and zero-crossing detector applications. However, it does not include the positive rail — inputs must stay at least 1.5 V below V+. For rail-to-rail input, use the LMV393 or TLV3201.

Common uses: window comparators (two LM393 halves bracket high and low thresholds), battery low-voltage disconnect, IR receiver signal shaping, relaxation oscillators, missing-pulse detectors, and level-triggered alarms.

Shenzhen stock is abundant — LM393 is one of the highest-volume comparators in the world, second-sourced by ST, onsemi, and every major Asian vendor. TI LM393AIDR (SOP-8) MOQ 2,500 pcs on reel, or 100 pcs loose.