LM311 – Voltage Comparator

The LM111, LM211 and LM311 are voltage comparators that have input currents nearly a thousand times lower than devices like the LM106 or LM710. They are also designed to operate over a wider range of supply voltages: from standard ±15V op amp supplies down to the single 5V supply used for IC logic.

LM311 – Voltage Comparator

LM311 - Voltage Comparator

Both the inputs and the outputs of the LM111, LM211 or the LM311 can be isolated from system ground, and the output can drive loads referred to ground, the positive supply or the negative supply. Offset balancing and strobe capability are provided and outputs can be wire ORed.

  • Operates from single 5V supply
  • Input current: 150 nA max. over temperature
  • Offset current: 20 nA max. over temperature
  • Differential input voltage range: ±30V
  • Power consumption: 135 mW at ±15V

Related Resources –

Voltage Comparator Information And Circuits

This page provides basic information about voltage comparator integrated circuits and is to act as reference material for other circuits. The circuits shown are based on the LM339 Quad Voltage Comparator chip or the LM393 Dual Voltage Comparator chip. These devices are functionally the same. The LM311 Voltage Comparator can be used for these applications as well but it also has a number of unique features.

Comparators and Schmitt Triggers

An LM311 in a comparator circuit is shown at the right, with the pin numbers for the connections. The open-collector output is at pin 7, and the ground for this transistor is at pin 1. It is shown pulled up to the logic voltage of +5 with a 1k resistor, which is typical. The output of the LM311 can sink 8 mA. A comparator’s output is essentially binary, YES or NO.

Quad-Differential-Comparator-LM339-TI

These devices consist of four independent voltage comparators that are designed to operate from a single power supply over a wide range of voltages. Operation from dual supplies also is possible, as long as the difference between the two supplies is 2 V to 36 V, and VCC is at least 1.5 V more positive than the input common-mode voltage.

Quad General Purpose Differential Comparator – LM339

An application from an old TI datasheet showing the versatility of this comparator. For me it was a workhorse and like LM324 was used in many products.

Quad General Purpose Differential Comparator - LM339
Current drain is independent of the supply voltage. The outputs can be connected to other open-collector outputs to achieve wired-AND relationships.

Differential to TTL convertor using LM339

  • Single Supply or Dual Supplies
  • Wide Range of Supply Voltage:
  • Low Supply-Current Drain Independent of Supply Voltage… 0.8 mA Typ
  • Low Input Bias Current …25 nA Typ
  • Low Input Offset Voltage . . . 2 mV Typ
  • Common-Mode Input Voltage Range Includes Ground
  • Differential Input Voltage Range Equal to Maximum-Rated Supply Voltage . . . ±36 V
  • Low Output Saturation Voltage
  • Output Compatible With TTL, MOS, and CMOS

Basic Analog for Digital Designers

“There is a long gap between engineering college and mid career in a non-engineering position, but technology marches on so a simple method of keeping abreast with the latest developments is required. This application note starts with an overview of the basic laws of physics, progresses through circuits 1 and 2, and explains op amp operation through the use of feedback principles.”

Basic Analog for Digital Designers – Application Note

Basic Analog for Digital Designers

AN9510.2 October 19, 2004 – This is an Analog Reference for the Embedded Engineer. An Application Note from Intersil Tech Reference.

  1. Basic Physics Laws, Circuit Theorems and Analysis
  2. Ohm’s and Kirchoff’s Laws
  3. Voltage and Current Dividers
  4. Thevenin’s and Norton’s Theorems
  5. Networks in the Feedback Path
  6. Types of Opamp Configurations
  7. Video Amplifiers

Conclusion

Some algebra, the basic laws of physics, and the basic circuit laws are adequate to gain an understanding of op amp circuits. By applying these tools to various circuit configurations it is possible to predict performance. Further in-depth knowledge is required to do op amp design, and there are many sources where this knowledge can be obtained. Don’t hesitate to try some of these tricks on your local circuit design engineer, but be aware that it may result in a long lecture about circuit design.

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