LM393G-S08-R — Dual Differential Voltage Comparator (SOP-8) from UTC

What Are the Technical Specifications of LM393G-S08-R?

Key numbers that matter: the 2V floor lets it sit on a battery rail that's almost flat. The open-collector output is the design constraint most engineers forget — it sinks, never sources, so the pull-up resistor decides the high level. But why does that single resistor trip up so many boards?

The 5mV offset is the practical resolution limit: two inputs within 5mV of each other are indistinguishable, which is why threshold circuits add hysteresis instead of pushing the offset.

When Should You Use (and NOT Use) the LM393G-S08-R?

✅ Use LM393G-S08-R when:

• You're comparing two voltages against a threshold. Battery monitors, over-voltage locks, thermostat trip points — the comparator's whole job is a clean high/low decision.
• Single-supply 3.3V or 5V logic rails. The 2V minimum covers everything down to a nearly-dead Li-ion cell, and the open-collector output drives TTL, DTL, and CMOS inputs directly.
• High-impedance sensing. The 25nA bias current means a 100kΩ divider chain barely loads the node it measures.
• Level shifting between different logic rails. Pull the output up to 3.3V while the comparator runs at 12V — the open collector makes rail conversion free.
• LM393-family drop-in. UTC, TI, ST, and NXP versions share the same 8-pin layout in DIP and SOP — swap sources without a board change.

❌ Don't use LM393G-S08-R when:

• You need an amplifier, not a comparator. A comparator has no frequency compensation; run it closed-loop and it oscillates. That's what the LM358G is for.
• Your input must swing near the positive rail. Common-mode tops out at V_CC − 1.5V. Rail-to-rail input comparators (TLV3701-class) cover the top 1.5V instead.
• You need a push-pull output. The LM393 only sinks. For a logic output that drives high without a pull-up, look at push-pull comparators like the TLC3702.
• Fast switching beyond ~1MHz. The 350ns response is fine for power and battery logic, but class-D or HF threshold work needs a faster comparator (TLV3501: 4.5ns).

What Are the Alternatives to LM393G-S08-R?

The LM393G vs LM393DR decision in one line: identical silicon behavior, different price and logo. The UTC part is what volume boards in Shenzhen actually carry; the TI part matters when your customer requires a branded source. Which one actually lands on your BOM?

Need four thresholds instead of two? Step up to the LM339 — same electrical core, four channels in a 14-pin package.

What Are the Typical Applications of LM393G-S08-R?

Battery undervoltage and overvoltage monitoring: a divider chain senses the pack, a reference sets the trip, hysteresis stops the annoying "click on, click off" at the boundary. The 2V floor keeps the monitor alive while the pack is nearly empty — a 2.5V reference and a 2V rail still leave headroom.

Window comparators for sensor validation: two comparators, one reference above and one below, and the output flags when the signal leaves the band. The LM393G is the classic two-channel part for exactly this — the second channel is already there.

Level translation between rails: comparator at 12V, output pulled up to 3.3V, and the MCU sees clean logic. The open collector makes this a two-resistor job with no level-shifter IC.

Relaxation oscillators and pulse generators: a capacitor charges through a resistor, the comparator flips at the trip points, and the output square wave drives buzzers, timers, or fan tach simulators. The 350ns response keeps oscillation accurate into the hundreds of kHz.

Why Buy LM393G-S08-R from ICMASS?

Every lot tested for offset and saturation voltage. We batch-test input offset and V_OL on LM393Gs before shipping. The most common counterfeit is a re-marked older die — it passes a continuity test but shows 10–20mV offset, which silently shifts your threshold.

Cross-reference support for the whole comparator family. Not sure whether the design wants LM393G, LM393DR, or LM339DR? Send us your channel count, supply voltage, and switching speed — we'll tell you which part the board actually needs.

BOM consolidation for monitor and protection boards. The same product usually carries a TL431 reference, a 78L05 regulator, and the LM393G. One shipment from Shenzhen covers the whole control section.

Same-day dispatch, 5–10 days worldwide. Orders before 15:00 CST ship same day via DHL or FedEx. For volume orders, we source directly from the UTC production line.

Frequently Asked Questions About LM393G-S08-R

Q1: My LM393 output never goes high — what's wrong?

A: The pull-up resistor is missing or not connected to the right rail. The output is open-collector: it only pulls low, and something external must pull it high. Add a 2.2k–10k resistor from the output pin to V_CC. This is the single most common LM393 failure reported on electronics forums.

Q2: The output edge is slow and rounded — why?

A: The pull-up value is too high for the frequency. The rise time is the pull-up resistor times the stray capacitance. At 200kHz, a 10k pull-up produces a rounded, unusable waveform; drop to 2.2k (or 680Ω for fast edges) and the square wave comes back.

Q3: The output oscillates when the inputs are close together — what causes this?

A: Noise near the threshold is flipping the comparator — add hysteresis. A resistor (470k–1M) from the output back to the non-inverting input creates a dead band. This is the standard fix discussed in comparator threads on Stack Exchange and All About Circuits.

Q4: The comparator misbehaves when the input is near V_CC — why?

A: The common-mode range stops at V_CC − 1.5V. Drive the input above that and the comparator can reverse polarity or oscillate. Keep inputs at least 1.5V below the rail, or switch to a rail-to-rail input comparator (TLV3701-class).

Q5: My threshold drifts between units — could it be the comparator?

A: Yes — the 5mV max offset shifts the trip point. With a 10k/10k divider on a 5V rail, 5mV of offset moves the threshold about 10mV. That's normal spec, not a fault. For tighter thresholds, use larger divider ratios or a comparator with lower offset.

Q6: Do I really need a 100nF decoupling capacitor?

A: Yes — right across V_CC and GND, close to the chip. The comparator switches in 350ns, and the current spike from that edge needs a local reservoir. Without it, high-speed oscillation and false triggers are common, especially near other switching circuits.

Q7: What should I do with the unused comparator inputs?

A: Tie them to ground. One input to GND and the other to a known level (GND or V_CC) prevents the unused half from oscillating and injecting noise into the used half. Never leave comparator inputs floating.

Q8: Can I use the LM393 as an op-amp?

A: No — a comparator is built for open-loop decision, not linear gain. Without internal frequency compensation, closed-loop operation oscillates. If you need gain, use an op-amp like the LM358G; if you need a clean threshold decision, the LM393 is the right tool.

Q9: Can the LM393 output drive an LED directly?

A: Yes — it sinks 18mA typical (6mA guaranteed). Connect the LED between the output and V_CC with a series resistor; the LED lights when the output is low. Note the output can't source current — it only pulls low, so the LED goes to the positive rail, not to ground.

Q10: LM393 vs LM339 — which one should I use?

A: Two channels → LM393; four channels → LM339. Same electrical core, same open-collector output, same 2V–36V range. The LM339's 14-pin package costs more board area, so pick it only when you genuinely need all four thresholds.