LM339

The LM339 is a quad differential voltage comparator IC that contains four independent high-gain comparators inside one package. Each comparator compares two input voltages and provides an open-collector output suitable for TTL, CMOS, or higher-voltage loads.

It operates over a wide supply range, has low power consumption, and can sense signals close to ground — making it perfect for single-supply embedded systems (5V, 12V, 24V, etc.).

Think of it as:

🔹 4 × LM393 channels
🔹 in one 14-pin chip

✨ Key Features

✅ Four independent comparators
✅ Wide supply: 2V → 36V (single supply)
✅ Low current consumption (~1 mA total)
✅ Open-collector outputs
✅ Ground-sensing inputs
✅ TTL / CMOS compatible
✅ Low cost & very robust

📊 Electrical Specifications
Parameter Typical / Range
Number of comparators 4
Supply voltage (Vs) 2 – 36 V (single) or ±1 – ±18 V
Supply current ~0.8–1 mA (total)
Input offset voltage ~2–5 mV
Input bias current ~25 nA
Propagation delay ~1–1.5 µs
Output type Open-collector
Output sink current up to 16–20 mA
Input common-mode includes ground
Operating temp 0°C to 70°C (LM339N/P commercial)
Package DIP-14, SOIC-14, etc.
🔌 Pin Configuration (DIP-14)
LM339
┌───────────┐
1 OUT1 VCC 14
2 IN1- OUT4 13
3 IN1+ IN4- 12
4 IN2+ IN4+ 11
5 IN2- IN3+ 10
6 OUT2 IN3- 9
7 GND OUT3 8
└───────────┘

⚙️ How the Output Works (important!)

Just like LM393:

👉 Open-collector output

Meaning:

LOW → actively pulled to GND

HIGH → needs external pull-up resistor

So always add:

Output ── 4.7kΩ ── Vcc

Without this, output won’t go HIGH properly.

🛠️ Common Applications

This chip shows up everywhere:

🔹 Practical uses

Battery level indicators

Sensor threshold detection

Window comparators

Zero-crossing detection

Over/under-voltage protection

PWM generation

Oscillators

Temperature monitoring

Motor control feedback

ADC front-ends

🧠 LM339 vs LM393 (quick comparison)
Feature LM393 LM339
Comparators 2 4
Package 8-pin 14-pin
Power lower slightly higher
Best for small circuits multi-channel systems
💡 Quick Tip

If you’re designing:

1–2 comparisons → LM393

3–4 comparisons → LM339

Many → LM339 saves board space + cost