LM393 Dual Comparator vs. LM358 Dual Op-Amp: Are they interchangeable?

LM393 Overview

The LM393 is a Dual in package comparator IC, meaning the IC has two comparators inside a single 8-pin package. The LM393 IC can be considered as the equivalent comparator version of the most popular LM358 Op-Amp. While any Op-Amp can be made to work as a voltage comparator, the LM393 proves itself to be advantages by providing an open collector output making it suitable to drive loads.

The LM393 series are dual independent precision voltage comparators capable of single or split supply operation. These devices are designed to permit a common mode range−to−ground level with single supply operation. Input offset voltage specifications as low as 2.0 mV make this device an excellent selection for many applications in consumer, automotive, and industrial electronics.

LM358 Overview

LM358 is a dual op-amp IC integrated with two op-amps powered by a common power supply. It can be considered as one half of LM324 Quad op-amp which contains four op-amps with common power supply. The LM358 series consists of two independent, high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages.

Utilizing the circuit designs perfected for Quad Operational Amplifiers, these dual operational amplifiers feature low power drain, a common mode input voltage range extending to ground/V_EE, and single supply or split supply operation. The LM358 series is equivalent to one−half of an LM324. These amplifiers have several distinct advantages over standard operational amplifier types in single supply applications.

LM393 vs. LM358: Pinout

Although the input specifications seem similar, it is clear that the LM358 Op-Amp has a lower bias current and offset voltage, since it is designed to be used as an amplifier where these parameters matter. On the other hand, the LM393 has slightly worse input bias and offset performance, because for a comparator these parameters are not usually critical, since it is designed to be used only to compare voltages and not amplify them.

This is also reflected in the large signal voltage gain. The op-amp has a smaller gain, whereas the comparator's gain is much higher to make the output transition as fast as possible. The bandwidth of the comparator is also not specified, since it is not compensated.

LM393 Features

● Wide Single−Supply Range: 2.0 Vdc to 36 Vdc

● Split−Supply Range: ±1.0 Vdc to ±18 Vdc

● Very Low Current Drain Independent of Supply Voltage: 0.4 mA

● Low Input Bias Current: 25 nA

● Low Input Offset Current: 5.0 nA

● Low Input Offset Voltage: 5.0 mV (max)

● Input Common Mode Range to Ground Level

● Differential Input Voltage Range Equal to Power Supply Voltage

● Output Voltage Compatible with DTL, ECL, TTL, MOS, and CMOS Logic Levels

● ESD Clamps on the Inputs Increase the Ruggedness of the Device without Affecting Performance

● NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements;                     AEC−Q100 Qualified and PPAP Capable

● These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS Compliant

LM358 Features

● Short Circuit Protected Outputs

● True Differential Input Stage

● Single Supply Operation: 3.0 V to 32 V

● Low Input Bias Currents

● Internally Compensated

● Common Mode Range Extends to Negative Supply

● Single and Split Supply Operation

● ESD Clamps on the Inputs Increase Ruggedness of the Device without Affecting Operation

● Pb−Free Package May be Available. The G−Suffix Denotes a Pb−Free Lead Finish

LM393 Comparator Internal Circuit

LM358 Op-Amp Internal Circuit

At first glance, the internal circuits of the LM358 and the LM393 look similar, but taking a closer look we can find the differences that explain the different specifications mentioned above.

The input stages are similar to "Darlington-connected" PNPs, which explains the ground sensing capability of both the LM358 and LM393. The differential stages run at different currents, however – the LM393 runs at a higher current to increase the gain and output switching speed. Since the LM358 is a linear amplifier, this is not so important.

The largest difference is the output stages. The output stage of the LM393 is much simpler than that of the LM358 because it is designed to switch the output between the rails as fast as possible, spending the smallest amount of time between the rails. The output stage is also open-collector. The LM358 has a fully linear output stage, since it is an op-amp and designed to be used as a linear amplifier, where the output scales linearly with the input.

LM393 Applications

● Voltage Comparator Circuits

● Can drive Relay, Lamp, Motor Etc

● Peak Voltage Detector

● High Voltage Protection/Warning

● Oscillator Circuits

● Zero Crossing Detector (Single Supply)

● Zero Crossing Detector (Split Supply)

● Free−Running Square−Wave Oscillator

● Time Delay Generator

● Comparator with Hysteresis

LM358 Applications

● Transducer Amplifiers

● Conventional Op-amp Circuits

● Integrator, Differentiator, Summer, Adder, Voltage follower, etc.,

● DC gain blocks, Digital multimeters, Oscilloscopes

● Comparators (Loop control & regulation)

● Active Filters

● General Signal Conditioning and Amplification

● 4- to 20-mA Current Loop Transmitters

LM393/LM358 SOIC−8 Package 

The LM358 and LM393 might seem outwardly similar, but the LM358 is an operational amplifier with linear output, and the LM393 is a comparator with a digital output, and they cannot be interchanged.

LM393 Datasheet

LM358 Datasheet

LM393 - Low Offset Voltage Dual Comparator IC

LM358 Dual Op-Amp: Pinout, Equivalent and Datasheet