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LM339 Quad Comparator

Four open-collector comparators. Same package as the LM324 quad op-amp, but a different pinout.

Cheat sheet (SVG)

Logic level: 2-36 V single or +/-1-18 V split
Package: PDIP-14 / SOIC-14

1.Pinout diagram

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Pins 1-7

LM339

Pins 8-14

Pin detail

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Logic level: 2-36 V single or +/-1-18 V split
Package: PDIP-14 / SOIC-14

Fig. 1. LM339 Quad Comparator, PDIP-14. Hover or tap a signal to light up every pin that carries it.

2.Watch out

VCC is pin 3 and GND is pin 12. The LM324 in the same package uses pins 4 and 11. Dropping an LM339 into an LM324 socket connects power to two inputs.
All four outputs are open collector and do nothing without a pull-up. Tie several together on one pull-up for a wired-AND, which is how multi-channel fault detectors are built.
With no hysteresis a slow input chatters. Add positive feedback from output to the non-inverting input, a few hundred k, for a Schmitt trigger. Nearly every real circuit needs it.
Two comparators plus one AND gate gives you a window comparator, which is the classic use for a quad part.
Input common mode goes to ground but stops about 1.5 V below V+, same as the LM393 and LM324.
The LM393 is two of these in a DIP-8 with the same arrangement as the LM358.

3.Comparator with hysteresis

What has to go around the chip before it will run.

Fig. 2. Comparator with hysteresis, drawn from Table 1. Dashed parts are optional. Crossing wires are not connected.

Table 1. External parts, and why each one is there.
Part	Between	Why
10 kOhm	OUT1 (2) to VCC	Open-collector output. Nothing inside the part pulls it up.
1 MOhmoptional	OUT1 (2) to IN1+ (5)	Positive feedback from the output back to the non-inverting input, for a clean single transition.
100 nF	VCC (3) to GND	Supply decoupling at the pin.

Four comparators sharing one supply pin. Unused inputs still need to be tied somewhere: a floating pair can swing the output and inject noise into the others through the supply.

4.Full pin reference

Every pin, alias and mapping. This is the table that prints.

Table 2. Pin assignments.

Complete pin reference for LM339 Quad Comparator
Pin	Name	Also called	Functions	Notes
1	OUT2	-	Comparator 2 output	Open collector. Needs a pull-up.
2	OUT1	-	Comparator 1 output	Open collector. Needs a pull-up.
3	VCC2-36 V	-	Positive supply	Pin 3, where the LM324 has an input. 100 nF to ground.
4	IN1-ADC	-	Comparator 1 inverting input
5	IN1+ADC	-	Comparator 1 non-inverting input
6	IN2-ADC	-	Comparator 2 inverting input
7	IN2+ADC	-	Comparator 2 non-inverting input
8	IN3-ADC	-	Comparator 3 inverting input
9	IN3+ADC	-	Comparator 3 non-inverting input
10	IN4-ADC	-	Comparator 4 inverting input
11	IN4+ADC	-	Comparator 4 non-inverting input
12	GND	V-	Negative supply	Pin 12, where the LM324 has an input.
13	OUT4	-	Comparator 4 output	Open collector.
14	OUT3	-	Comparator 3 output	Open collector.

Primary sources

TI LM339 datasheet ↗

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