LM339 Voltage Comparator: Features, Applications, and How to Use It
2024-11-29 300

The CD74HCT20M is a high-performance CMOS logic dual 4-input NAND gate. By employing silicon gate CMOS technology, these logic gates deliver operating speeds akin to LSTTL gates while maintaining the energy efficiency characteristic of standard CMOS integrated circuits. They frequently find application in diverse contexts such as buffer circuits, logic inverter circuits, and more.

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LM339 Pin Configuration

LM339 Features and Electrical Characteristics

The LM339 contains four independent voltage comparators. Each comparator operates individually, ensuring that the performance of one does not affect the others. This feature minimizes noise interference between comparators, which is crucial in sensitive circuits where accuracy matters.

The chip can work with a single power supply or a dual power supply. With a single supply, it operates within a voltage range of +3.0 V to +36 V. When using dual supplies, it can handle a range of +18 V and -18 V. This flexibility makes the LM339 versatile for different applications where power requirements vary.

For the input side, the LM339 is designed to minimize any bias current. The input bias current is as low as 25 nA, which helps in applications where even tiny currents could cause errors in the system. The input offset current is also very low, at just ±5.0 nA, further enhancing precision.

The input offset voltage is kept low, ensuring that even very small voltage differences are accurately detected. The input common-mode voltage range extends all the way to ground, meaning the LM339 can handle signals that start from zero volts, which is beneficial in many low-voltage applications.

The LM339 also boasts a very low output saturation voltage, just 130 mV at a 4.0 mA load current. This is important for low-voltage applications, like battery-powered circuits, where you want to minimize the power lost through the device. The reduced saturation voltage ensures that the output remains usable even when the system is running on minimal power.

The device is fully compatible with TTL and CMOS logic levels, making it easy to integrate with various digital systems without the need for additional components or level shifting.

To ensure reliable operation, the LM339 includes ESD (Electrostatic Discharge) clamps on its inputs. These clamps protect the device from static discharge that could otherwise damage the chip, all while ensuring the device functions normally.

In terms of environmental standards, the LM339 is Pb-free, halogen-free, and RoHS-compliant. These features make it a suitable choice for modern electronics that must meet strict environmental and safety regulations.

Similar to LM339 Voltage Comparators

LM311, LM324, LM397, LM139, LM239, LM2901 etc.

LM339 IC Overview

The LM339 is commonly used in circuits where you need to compare two voltage signals. It’s a versatile device because it contains four separate comparators, allowing it to compare four pairs of voltage signals simultaneously. This feature is especially useful in applications where you need to monitor multiple voltage levels at once, such as in power supply monitoring, voltage threshold detection, and signal processing tasks.

What makes the LM339 popular among engineers and makers is its combination of low cost and solid performance. The chip is designed to be reliable without breaking the budget, which is why it’s a go-to choice for many DIY projects and industrial applications. Its cost-effectiveness doesn’t mean it compromises on functionality; the comparators offer decent speed and accuracy for a wide range of tasks.

The LM339’s response time is fast enough to meet the needs of most applications. Whether you’re designing a simple voltage comparator circuit or something more complex, the IC’s performance can handle most real-time voltage detection needs without noticeable delays.

In practical use, the ability to compare multiple voltage pairs at once can simplify circuit design and save board space. This is especially valuable in systems that need to compare several voltage signals in parallel without requiring separate components for each pair.

Overall, the LM339 offers a straightforward, efficient solution for voltage comparison, whether in basic applications or more advanced designs that demand quick and reliable performance.

How to Use the LM339 Voltage Comparator

Let’s break down the functionality of the LM339 by looking at its internal structure. The LM339 contains four independent comparators, which means it can compare multiple voltage signals simultaneously. Each comparator is connected internally to allow for parallel voltage comparisons, making the IC a flexible solution for various applications.

Now, let’s focus on just one of those comparators and build a simple application circuit to see how it works. In this basic setup, we will compare two input voltages, V1 and V2, and generate an output based on which voltage is higher.

In this circuit, the LM339 compares the two voltages—V1 and V2. The result of this comparison is output as Vo. The device is powered by a single voltage source, VCC, as shown in the diagram.

The LM339 operates as follows:

If V1 is greater than V2, the output Vo will be at VCC (the supply voltage).

If V2 is greater than V1, the output Vo will be 0V (or GND).

This setup is useful for determining which of the two voltages is higher. The output (Vo) directly reflects the result of the comparison. A high output (VCC) indicates that V1 is higher, while a low output (0V) means V2 is higher.

When you’re building this circuit in a real-world application, you’ll notice that the LM339’s output is “clean” and responds quickly to changes in input voltage. It’s important to ensure that both input voltages (V1 and V2) are within the specified range for the comparator to function correctly. If either input exceeds the operating voltage limits, it could lead to inaccurate comparisons or damage to the IC.

Applications of LM339

Oscillators

The LM339 is frequently used in oscillator circuits, where it helps generate a stable frequency. When designing an oscillator, you can use the LM339 to compare voltages and control the switching action. Its fast response time and low power consumption make it ideal for generating clock pulses or waveform signals in various electronic systems.

Voltage Comparators

As a voltage comparator, the LM339 is designed to compare two input voltages and determine which is higher. It’s widely used in applications where precise voltage level detection is required, such as in battery-powered devices or circuits that need to monitor voltage levels continuously. Its ability to operate over a wide voltage range adds versatility to different designs.

Peak Detectors

The LM339 can also be employed in peak detection circuits. In audio systems or measurement applications, you often need to capture the highest point of a fluctuating signal. The LM339’s accuracy allows it to detect and hold the peak value, making it useful for monitoring signal levels in audio processing, test equipment, and signal analyzers.

Logic Voltage Translation

In systems where different parts of the circuit operate at different voltage levels, the LM339 can be used to translate logic signals between them. This is particularly helpful when interfacing devices that run on varying logic voltages, ensuring smooth communication between different systems without signal distortion.

Power Supervision

The LM339 can also play a critical role in power supervision circuits. It can monitor the power supply’s voltage and trigger actions such as shutting down or switching to backup power when voltage levels go out of range. This is essential in systems where reliable power is crucial, such as in safety devices or remote monitoring systems.

Industrial Applications

In industrial environments, the LM339 is commonly used for monitoring parameters like temperature, pressure, or other sensor data. Its ability to perform accurate voltage comparisons makes it perfect for interfacing with industrial sensors and controlling alarms or safety protocols when thresholds are exceeded.

Measuring Instruments

In measuring instruments like voltmeters and multimeters, the LM339 is used to compare voltage levels and ensure accurate readings. It’s an essential component for circuits that need stable and precise voltage comparisons, especially in portable testing equipment or instruments used in the field.

Automotive

The automotive industry uses the LM339 for various monitoring applications. It’s commonly found in systems that monitor battery voltage, engine parameters, and other critical aspects of vehicle performance. Its robustness in handling wide voltage ranges and fast response times makes it a reliable choice for automotive control systems.

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Datasheet PDF

LM339 Datasheets