LM393 vs LM358: Which IC Should You Choose for Your Circuit?

What's the difference between the LM393 and the LM358? It's one of the most-searched questions in analog electronics — and for good reason. These two dual-channel ICs share the same package, the same pinout, and even appear side by side in countless Arduino sensor modules. Yet using the wrong one can quietly sabotage your circuit with sluggish response times, missing output signals, or unstable behavior. In this guide, we'll cut through the confusion and show you exactly which IC belongs in your next project — and why.

Quick Answer: LM393 vs LM358 at a Glance (Comparison Table)

If you're short on time, here's the bottom line:

• The LM358 is a dual operational amplifier (op-amp) designed for linear signal processing — amplification, filtering, and sensor conditioning.
• The LM393 is a dual voltage comparator designed for digital decision-making — comparing two voltages and producing a HIGH or LOW output.

Use the LM358 when you need to shape an analog signal. Use the LM393 when you need to decide between two voltage levels.

LM393 vs LM358: Core Technical Differences

While the LM393 and LM358 may look like twins on a schematic, their internal designs reveal two very different philosophies. Understanding these differences is the key to choosing the right IC — and avoiding frustrating debugging sessions later. Let's break down the four most important technical distinctions.

1. Op-Amp vs Comparator: The Functional Divide

The most fundamental difference between these two ICs lies in what they were designed to do.

The LM358 is a general-purpose operational amplifier. It's built for linear operation, meaning its output is intended to be a continuous, proportional response to its input. With external feedback resistors, the LM358 can amplify, filter, integrate, or differentiate analog signals with predictable, stable behavior.

The LM393 is a dedicated voltage comparator. It has no internal compensation capacitor and is not designed to be used with negative feedback. Its job is binary: compare the voltage at the non-inverting input (V+) to the voltage at the inverting input (V−), and drive the output either fully ON or fully OFF based on which is greater.

In short: the LM358 produces a smooth analog output; the LM393 produces a digital-style switching output.

2. Output Stage: Push-Pull vs Open-Collector

This is the difference that trips up the most engineers — and it has major implications for how you wire each IC into a circuit.

The LM358 features a push-pull (Class AB) output stage. This means the output can actively source current to pull HIGH or sink current to pull LOW, all on its own. You can connect its output directly to the next stage of your circuit without additional components.

The LM393, by contrast, uses an open-collector output. The internal transistor can only pull the output LOW (to ground); it cannot drive the output HIGH on its own. To get a usable HIGH signal, you must connect an external pull-up resistor between the output pin and your positive supply rail (typically 4.7 kΩ to 10 kΩ).

The advantage of the open-collector design is flexibility: you can pull the output up to any voltage within the IC's rating, making the LM393 ideal for interfacing between different voltage domains (for example, a 12 V analog circuit driving a 5 V or 3.3 V microcontroller input). Multiple LM393 outputs can also be wire-OR'd together — something a push-pull op-amp cannot do.

3. Speed: Slew Rate vs Response Time

If your circuit needs to react quickly to changing signals, this difference matters enormously.

The LM358 has a slew rate of approximately 0.3 V/µs, which is relatively slow by modern standards. This is fine for audio-frequency applications, low-bandwidth sensor signals, and DC-coupled amplification, but it means the LM358 will struggle with fast-edge signals or high-frequency switching.

The LM393 boasts a typical response time of around 1.3 µs, making it dramatically faster at transitioning between output states. This makes it ideal for applications like square-wave generation, zero-crossing detection, and fast threshold triggering.

If you tried to use an LM358 as a comparator in a high-speed application, the slow slew rate would round off your edges, introduce delay, and potentially cause oscillation near the threshold — a classic beginner mistake.

4. Power, Precision, and Input Characteristics

Both ICs are remarkably power-efficient and operate over a wide voltage range, but with subtle differences:

The LM358 operates from 3 V to 32 V (single supply) or ±1.5 V to ±16 V (dual supply), drawing about 0.7 mA of quiescent current. Its input offset voltage is typically 2 mV, which is acceptable for most general-purpose amplification but not ideal for precision instrumentation.

The LM393 operates over a slightly wider range — 2 V to 36 V single supply — and draws even less current at around 0.4 mA. Its input offset voltage is typically 1 mV, giving it a slight edge in threshold accuracy. Both ICs share the same input common-mode range that includes ground, which is what makes them so popular in single-supply battery-powered designs.

Why These Differences Matter in Practice

Imagine you're building a light-activated switch using an LDR (light-dependent resistor). If you use an LM393, the output will snap cleanly from LOW to HIGH the moment the light level crosses your threshold — perfect for triggering a relay or microcontroller pin. If you mistakenly use an LM358 without feedback, the output will try to behave like a comparator, but the response will be slow, the transition will be mushy, and the output won't reach the supply rails. The circuit might work — sort of — but it won't be reliable.

This is why understanding the intent behind each IC is more important than just matching pin numbers.

Pinout Comparison: Are They Pin-Compatible?

This is one of the most common questions engineers ask when first comparing the LM393 and LM358 — and it's also where the most dangerous misconceptions live. The short answer is: the pinouts are physically identical, but the ICs are not functionally interchangeable. Let's unpack what that really means.

Identical Pin Layout

Both the LM393 and LM358 come in the same standard 8-pin packages (DIP-8, SOIC-8, TSSOP-8, and others), and their pin assignments map one-to-one:

If you laid the two datasheets side by side, you'd see that every pin serves the same positional role. This is why you'll often hear hobbyists say the two chips are "pin-compatible" — and from a purely mechanical standpoint, they are. You can drop an LM393 into a socket designed for an LM358 (or vice versa) without bending a single lead.

Why "Pin-Compatible" Doesn't Mean "Interchangeable"

Here's where the trap lies. Even though the pins line up perfectly, the electrical behavior of those pins is fundamentally different, primarily because of the output stage difference we covered in the previous section.

Consider what happens if you swap an LM358 for an LM393 in an existing circuit:

• No pull-up resistor on the output? The LM393's open-collector output will never go HIGH. The circuit will appear "dead" even though the IC is working perfectly.
• Feedback network from output to inverting input? The LM358 expected this for stable linear operation. The LM393 doesn't have internal compensation and may oscillate, latch up, or behave erratically.
• Driving an analog load (like a speaker or sensor signal chain)? The LM393 cannot produce a smooth analog waveform — you'll get a square wave or no signal at all.

Now consider the reverse — swapping an LM393 for an LM358:

• Threshold detection circuit? The LM358's slow slew rate will cause sluggish, mushy transitions instead of crisp HIGH/LOW edges.
• Output expected to swing to the rails? The LM358 cannot pull its output all the way to V+ (it falls about 1.5 V short), which may not trigger downstream logic.
• Wire-OR connection with other comparators? The LM358's push-pull output will short-circuit against other outputs, potentially damaging the IC.

A Practical Rule of Thumb

Think of it this way: the package is a shipping container, but the cargo inside is completely different. Two trucks can have identical trailers, but if one is hauling refrigerated produce and the other is hauling cement, you can't swap the cargo without consequences.

When designing or repairing a circuit, always confirm the IC type by part number printed on the chip — never assume based on the socket or PCB footprint alone. Many counterfeit or mislabeled components in the wild use the same package, and substituting the wrong part can cause hours of debugging headaches.

When the Identical Pinout Is Useful

There is one scenario where the matching pinout works in your favor: prototyping and design flexibility. If you're developing a new product and aren't yet sure whether your application needs comparator behavior or op-amp behavior, you can design a single PCB footprint that accepts either chip. By populating the appropriate IC and adjusting a few external components (adding or removing a pull-up resistor, changing feedback networks), you can switch between linear and switching behavior without redesigning the board.

How to Choose the Right IC for Your Project?

Now that you understand the technical differences between the LM393 and LM358, the practical question becomes: how do you actually decide which one to use? The answer almost always comes down to a single question about your circuit's purpose. Let's walk through a clear decision framework, followed by typical use cases for each IC.

The One-Question Decision Test

Before looking at datasheets or comparing specs, ask yourself this:

"Do I need to shape a signal, or do I need to decide something based on a signal?"

• If the answer is shape — amplify, filter, buffer, or condition an analog waveform — you want the LM358.
• If the answer is decide — compare two voltages and produce a HIGH/LOW output — you want the LM393.

This single question resolves the vast majority of design decisions. The remaining edge cases usually involve speed requirements, output interfacing needs, or power constraints, which we'll cover in the checklist below.

A 5-Point Decision Checklist

When you're not sure which IC fits your application, run through these five questions in order:

1. What does the output need to look like?

A continuous, proportional analog signal → LM358. A binary HIGH/LOW switching signal → LM393.

2. How fast does the output need to respond?

Slow signals under a few kHz (audio, sensor conditioning) → LM358 is fine. Fast edges or microsecond-level transitions → LM393.

3. What voltage does the output need to drive?

The same voltage as the IC's supply rail → either works (LM358 with limitations near V+). A different voltage rail (e.g., 12 V circuit driving a 3.3 V MCU) → LM393 with a pull-up to the target rail.

4. Will the output connect to other outputs (wired-OR logic)?

Yes → LM393 (open-collector outputs are safe to tie together). No → either works.

5. Do you need feedback for stable, predictable amplification?

Yes → LM358 (designed for closed-loop operation). No → LM393 (designed for open-loop switching).

Typical Applications for the LM358

The LM358 thrives in low-frequency, single-supply analog signal processing. Its low cost, wide voltage range, and ground-referenced inputs make it the go-to choice for:

• Audio preamplifiers for microphones, electret capsules, and small signal sources
• Active filters (low-pass, high-pass, band-pass) in sensor signal chains
• Sensor signal conditioning for thermistors, photodiodes, gas sensors, and load cells
• Voltage followers and buffers to isolate high-impedance sources from low-impedance loads
• Summing and difference amplifiers in basic analog computation
• Battery-powered analog circuits where low quiescent current matters

If your project involves an analog sensor whose output needs to be amplified, smoothed, or scaled before reaching an ADC or microcontroller, the LM358 is almost always the right starting point.

Typical Applications for the LM393

The LM393 excels at fast, accurate threshold detection and binary decision-making. Its open-collector output and rapid response time make it ideal for:

• Light-activated switches using LDRs or photodiodes
• Temperature threshold alarms with thermistors or RTDs
• Battery low-voltage detectors that trigger an alert below a set voltage
• Zero-crossing detectors for AC waveform timing and dimmer circuits
• Square-wave and relaxation oscillators when paired with an RC network
• Window comparators that detect when a voltage falls within (or outside) a defined range
• IR obstacle and line-following sensors in robotics and automation
• Logic-level shifters between different voltage domains (e.g., 12 V industrial sensors to 3.3 V MCUs)

If your project's job is to take an analog input and answer a yes/no question about it, the LM393 is purpose-built for that role.

Special Cases and Trade-Offs

A few situations deserve extra consideration:

"Can I use the LM358 as a comparator?"

Technically yes, and many low-cost modules do exactly this to save BOM cost. But expect slow transitions, no rail-to-rail output, and potential oscillation near the threshold. Only acceptable for very slow, non-critical applications.

"Can I use the LM393 as an amplifier?"

No. The LM393 lacks internal frequency compensation and isn't designed for negative feedback. Attempting to use it as an op-amp will result in oscillation or unstable behavior.

"What if I need both functions in one circuit?"

Use both — they're inexpensive, share the same package footprint, and complement each other well. A common pattern is to use an LM358 to amplify a weak sensor signal, then feed that amplified signal into an LM393 to trigger a digital output when a threshold is crossed.

"What about modern alternatives?"

For new precision designs, consider rail-to-rail op-amps (like the MCP6002) or modern comparators (like the TLV3201) that offer better performance. But for cost-sensitive, general-purpose applications — especially in education, hobbyist projects, and industrial controls — the LM358 and LM393 remain unbeatable in price-per-performance.

Where to Source Reliable LM358 and LM393 ICs

Component authenticity matters more than most engineers realize. Counterfeit LM358 and LM393 chips are common in unverified marketplaces, and they often fail to meet datasheet specifications — leading to circuits that work intermittently or fail under load. For genuine, traceable components and ready-to-use breakout modules built around both ICs, browse the catalog at Unit Electronics, where you'll find both standalone ICs and pre-assembled sensor boards designed for prototyping and production use.

Frequently Asked Questions

Is the LM393 an op-amp?

No. The LM393 is a dual voltage comparator, not an op-amp. Although it shares the same 8-pin package and pinout as the LM358 op-amp, it lacks internal frequency compensation and uses an open-collector output designed for binary HIGH/LOW switching — not continuous analog signals.

Are the LM393 and LM358 pin-compatible?

The LM393 and LM358 have identical pin layouts in standard 8-pin DIP and SOIC packages, but they are not functionally interchangeable. Swapping one for the other without modifying the supporting circuitry — such as adding a pull-up resistor for the LM393 or feedback network for the LM358 — will cause the circuit to malfunction.

Do both ICs require a pull-up resistor?

No — only the LM393 requires a pull-up resistor (typically 4.7 kΩ to 10 kΩ between the output and V+) because of its open-collector output. The LM358 has a push-pull output stage that drives both HIGH and LOW on its own, so no pull-up is needed.

Conclusion: Final Recommendation

The LM393 and LM358 may share an identical pinout, but they solve fundamentally different problems. Choose the LM358 when your circuit needs to shape an analog signal — amplifying, filtering, or buffering a continuous waveform. Choose the LM393 when your circuit needs to decide on a signal — comparing two voltages and producing a clean HIGH/LOW output. If you remember just one rule: the LM358 shapes, the LM393 decides.

For reliable performance in any design, sourcing genuine components matters. Browse authentic LM358, LM393, and related analog ICs — along with ready-to-use breakout modules — at Unit Electronics.