LM339

LM339 is a quad voltage comparator IC. It contains four independent comparators in one package, each with a differential input and an open-collector output.
Key points:
- Output: open-collector, means the transistor can sink current but cannot source. Use pull-up resistors to a logic supply.
- Supply and inputs: typically operates from about 2 to 36 V. Input common-mode range includes ground and goes up to roughly Vcc minus a small margin (careful near the top rail).
- Operation: when V+ (non-inverting) > V− (inverting), the output transistor conducts (low); when V+ ≤ V−, the transistor is off and the pull-up pulls the output high.
- Pros and uses: cheap, simple threshold detectors, zero-cross detectors, window detectors, level shifters, and other comparator-based circuits.
- Limitations: no built-in hysteresis (can oscillate without feedback), must stay within common-mode range, external pull-ups required, and output can sink only a limited current per channel.
Commonly used in 0–5 V or 3–12 V logic interfaces, often in DIP14 or SOIC14 packages.

Key LM339 features (quad comparator):
- Four independent differential-input comparators in one package.
- Open-collector outputs (one per comparator); require pull-up resistors; can be wired-OR.
- Wide supply range: 2 V to 36 V (single or dual supply).
- Input common-mode range includes ground and goes up to about Vcc − 1.5 V.
- Outputs sink current (typical up to ~16 mA per channel); no output sourcing.
- Low power consumption; suitable for battery-powered apps.
- Small input bias currents and low input offset voltage (typical a few mV; bias in tens of nA range).
- Propagation delay in the microsecond range (depends on supply, load, and temperature).
- Industrial/commercial temp ranges (e.g., -40°C to +125°C for many parts).
- Package options: DIP-14, SO-14, TSSOP-14, etc.
- No internal hysteresis; external feedback can provide hysteresis if needed.
Common uses: level shifting, zero-crossing, window detectors, and simple threshold comparisons.

LM339 is a quad comparator IC. Common 14-pin packages include DIP-14 (through-hole) and SO-14 (surface-mount); also available in MSOP-14 and TSSOP-14.

- Pin count: 14 pins (DIP/SOIC, etc.). It contains four independent comparators (A, B, C, D) plus Vcc and GND pins.
- Function: Quad voltage comparator with open-collector outputs. Each comparator compares its non-inverting and inverting inputs; when V+ > V− the output sinks current (low); otherwise the output floats (high, via pull-up resistor). Typical supply range is 2–36 V.

The LM339 is manufactured by Texas Instruments (TI). TI is an American multinational semiconductor company that designs, manufactures, and sells analog and digital integrated circuits and related components (it acquired National Semiconductor in 2011).

LM339 is a quad voltage comparator with open-collector outputs.
Applications:
- Threshold/level detection: battery/power-supply monitoring, undervoltage/overvoltage protection
- Zero-cross and window detectors (AC sensing)
- Relay/LED/driver interfaces (sinking outputs with pull-ups)
- Digital interfacing and level shifting (wired-OR/AND)
- Timing and oscillators: relaxation oscillators, PWM, one-shot circuits
- Sensor front-ends and instrumentation (temperature, light, etc.)

LM339 is a quad voltage comparator with open-collector outputs. Common drop-in equivalents include:
- LM2901 (quad comparator, same family)
- LM239/LM239N (quad comparator)
- ST TS339 (quad comparator)
- Low-voltage variants: LMV339, TLV339 (TI)
- NTE/other vendor replacements (pin-compatible equivalents)
Always verify pinout, input common‑mode range, and open‑collector behavior before substitution.