Comparison between LM393 and LM311, which one to use?

 The LM393 and LM311 are two popular operational amplifier (op-amp) integrated circuits used in a variety of applications. Both are comparators, meaning they compare two input voltages and produce an output signal based on their comparison. In this article, we will compare these two devices and discuss their key differences.

 First, let's take a look at the input structure of the LM393 and LM311.The LM393 is a dual-comparator, meaning it contains two comparators in a single package. The LM311, on the other hand, is a single comparator with a more versatile input structure. The LM311 has an open-collector output, which makes it more versatile and useful in a wider range of applications.

The LM393 also has a more limited input range than the LM311. The LM393 has a maximum input voltage range of only a few volts, whereas the LM311 can handle input voltages up to 32V. This makes the LM311 a more suitable option for high voltage applications.

Another key difference between the two devices is their power consumption. The LM393 is designed to consume very low power, making it an ideal choice for battery-powered applications. The LM311, on the other hand, is designed to handle higher power requirements, making it a good choice for applications that require more power.

In terms of speed, both devices are quite fast, but the LM311 has a faster response time. The slew rate of LM393 is typically 0.5V/us while that of LM311 is 11 nV/Hz, depending on the version and configuration. LM311 has a faster slew rate compared to LM393. This makes the LM311 a better choice for applications that require fast and accurate voltage comparison. See Op-Amp usefulness based on unity-gain Bandwidth (GBW) and Slew Rate to learn more about speed limits of Op-Amp.

Finally, let's take a look at their cost. Both devices are very affordable and can be easily purchased from most electronics suppliers. However, the LM393 is generally more affordable than the LM311 due to its simpler input structure and lower power consumption requirements.

Let us compare their application area:

The LM311 is a voltage comparator integrated circuit (IC) with applications in:

  • Threshold Detection: used as a simple switch to detect a voltage level, providing a digital output signal indicating whether the input voltage is above or below a reference level.

  • Hysteresis Generation: adding hysteresis to a threshold detection circuit, to reduce unwanted oscillations around the threshold voltage.

  • Schmitt Trigger: a circuit that provides square wave output, with clean rising and falling edges, useful for converting noisy analog signals into clean digital signals.

  • Voltage-to-Frequency Conversion: used to convert an input voltage into an output frequency, useful for converting an analog signal into a digital signal.

  • Oscillator Design: used to design oscillators by providing a stable trigger input, which generates a periodic waveform output.

  • Amplifier Design: used as a buffer or amplifier to isolate different stages of a circuit, with a gain of unity.

 Some application area of LM393 comparator integrated circuit(IC) are as follows.

  • Comparator circuits
  • Window comparator circuits
  • Voltage level detection
  • Peak detectors
  • Zero crossing detectors
  • Clamped inductor waveform shaping
  • Power supply voltage supervision
  • DC level sensing and alarms
  • Voltage reference circuits
  • Switch mode power supplies (SMPS)
  • Ramp rate control for sawtooth generators.

In conclusion, both the LM393 and LM311 are versatile and useful comparators that can be used in a variety of applications. The LM393 is ideal for low-power applications with limited voltage requirements, while the LM311 is more suitable for high voltage and high power requirements with faster response time. The choice between these two devices will ultimately depend on the specific requirements of your application.

If you are interested in LM311 and LM393 op-amp applications see the following application tutorials.

- Inductance meter with Arduino and LM393

- LM393 light sensor circuit

- LM311 circuit examples

- Light sensor using LDR and LM311

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