TI / ON / many · Integrated circuit

LM393 Dual Comparator

Two comparators in the same DIP-8 arrangement as the LM358 op-amp, with open-collector outputs. The two look identical on a board and are not interchangeable.

Cheat sheet (SVG)

Logic level: 2-36 V single or +/-1-18 V split
Package: PDIP-8 / SOIC-8

1.Pinout diagram

Highlight a signalhover to preview, click to keep

Pins 1-4

LM393

Pins 5-8

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Logic level: 2-36 V single or +/-1-18 V split
Package: PDIP-8 / SOIC-8

Fig. 1. LM393 Dual Comparator, PDIP-8. Hover or tap a signal to light up every pin that carries it.

2.Watch out

The outputs are open collector. Without a pull-up resistor to your logic rail, nothing comes out at all. 10k is the usual choice; lower if the line is long or fast.
Same package and same pin arrangement as the LM358, which is why they get swapped by mistake. The LM358 is an op-amp with a push-pull output and will not work as a comparator at speed; the LM393 has no frequency compensation and will oscillate if you close a feedback loop around it.
With no hysteresis a slow input makes the output chatter across the threshold. Add positive feedback from output to the non-inverting input, a few hundred k, to turn it into a Schmitt trigger. Nearly every real comparator circuit needs this.
Open collector means you can wire several outputs together on one pull-up and get a wired-AND, which is how multi-channel alarm circuits are built.
Input common mode range goes down to ground but stops about 1.5 V below V+, the same limitation as the LM358.
The LM339 is four of these in a DIP-14, at the cost of a different pinout.

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 (1) to VCC	The output is an open collector. It can only pull low, so without this there is no high level at all.
1 MOhmoptional	OUT1 (1) to IN1+ (3)	Positive feedback. A few millivolts of hysteresis stops the output chattering as the inputs cross.
100 nF	VCC (8) to GND	Supply decoupling at the pin.

Open collector cuts both ways: it is why you can wire several outputs together as an AND, and why a comparator with no pull-up looks dead on a scope.

4.Full pin reference

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

Table 2. Pin assignments.

Complete pin reference for LM393 Dual Comparator
Pin	Name	Also called	Functions	Notes
1	OUT1	OUTA	Comparator 1 output	Open collector. Needs a pull-up.
2	IN1-ADC	INA-	Comparator 1 inverting input
3	IN1+ADC	INA+	Comparator 1 non-inverting input
4	GND	V-	Negative supply	Ground in a single supply circuit.
5	IN2+ADC	INB+	Comparator 2 non-inverting input
6	IN2-ADC	INB-	Comparator 2 inverting input
7	OUT2	OUTB	Comparator 2 output	Open collector. Needs a pull-up.
8	VCC2-36 V	-	Positive supply	100 nF to ground at the pin.

Primary sources

Found a wrong pin? The whole board is one file, data/boards/lm393.json.

Edit this file on GitHub Report it instead