The LM7824 voltage regulator is a fixed positive linear regulator that provides a constant 24V output from a higher input voltage. This article will discuss the LM7824 voltage regulator, including its specifications, internal functional block diagram, key features, operating circuits, applications, and many more.

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LM7824 Voltage Regulator Basic

The LM7824 is a fixed positive voltage regulator designed to provide a stable 24V DC output. It belongs to the popular 78XX series of three-terminal regulators, originally developed by Fairchild Semiconductor and now produced by ON Semiconductor. One common version of this regulator is the LM7824CT , which is packaged in a TO-220 case for easy mounting and better heat dissipation.

The LM7824 regulates a higher input voltage and converts it into a steady 24V output, making it useful for many electronic systems that require stable power. With proper heat sinking, it can deliver up to about 1A of output current. The regulator also includes built-in protection features such as internal current limiting, thermal shutdown, and safe operating area protection, helping protect the device from damage during operation.

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LM7824 Voltage Regulator CAD Models

LM7824 Voltage Regulator Pinout

Alternatives & Equivalent Model

• MC7824

• MC7824CT

• MC7824ACT

• UA7824

• L7824CV

• L7824CT

• KA7824

• NJM7824

• KIA7824

• <a href="https://www.y-ic.com/pdf/ST/L78S24CV.html" "="" target="_blank" style="cursor: pointer; color: rgb(0, 0, 238); font-weight: bold;">L78S24CV

LM7824 Functional Block Diagram

How the regulator controls and stabilizes the output voltage? The input voltage enters the circuit through Pin 1 and is passed to the series pass element, which acts like a control gate that adjusts the amount of voltage delivered to the output. By controlling this element, the regulator maintains a steady 24V output even when the input voltage or load current changes.

Inside the regulator, a reference voltage block generates a stable internal voltage used as a standard for comparison. The error amplifier compares this reference voltage with the actual output voltage. If the output voltage changes, the error amplifier sends a signal to the series pass element to increase or decrease conduction, bringing the output voltage back to the correct level.

The diagram also shows several protection circuits. The SOA protection block ensures the device operates within safe electrical limits, while the thermal protection circuit shuts the regulator down if the temperature becomes too high. A current generator and starting circuit help initialize and stabilize the internal operation of the regulator when power is first applied. These internal blocks work together to provide a stable and protected 24V regulated output.

LM7824 Voltage Regulator Specifications

LM7824 Voltage Regulator Features

Fixed 24V Output Voltage

The LM7824 provides a stable 24-volt regulated output, making it suitable for circuits that require a constant voltage supply. Once the proper input voltage is applied, the regulator maintains the output at 24V even if the input voltage or load conditions change.

Up to 1A Output Current

This regulator can supply up to about 1 ampere of output current when proper heat sinking is used. This allows the LM7824 to power medium-power electronic circuits such as control boards, industrial modules, and communication equipment.

Internal Current Limiting

The LM7824 includes built-in current limiting protection. If the load tries to draw too much current, the regulator automatically restricts the current flow to prevent damage to the device and the connected circuit.

Thermal Shutdown Protection

To protect the device from overheating, the LM7824 features thermal shutdown circuitry. If the internal temperature becomes too high, the regulator temporarily shuts down until the temperature returns to a safe level.

Safe Operating Area (SOA) Protection

The regulator also includes safe operating area protection, which helps keep the device working within safe voltage and current limits. This feature improves reliability and prevents failure during abnormal conditions.

Simple Three-Pin Design

The LM7824 uses a three-terminal configuration: input, ground, and output. This simple design makes it easy to use in power supply circuits without requiring many external components.

TO-220 Package for Better Heat Dissipation

The device is commonly available in a TO-220 package, which allows efficient heat dissipation. The metal tab can also be attached to a heat sink to improve thermal performance when higher current is required.

LM7824 Operating in Circuit

Basic DC Operation Circuit

This circuit shows the basic way to use the LM7824 voltage regulator. The input voltage is applied to Pin 1 (Input), while Pin 2 is connected to ground, and Pin 3 provides the regulated output. A 0.33µF capacitor (C₁) is placed at the input to reduce noise and stabilize the incoming voltage. A 0.1µF capacitor (C₀) is connected at the output to improve stability and prevent oscillation. When the input voltage is higher than the required level (usually above about 27V), the LM7824 regulates it and provides a steady 24V output. This simple configuration is commonly used in power supply circuits.

Load Regulation Circuit

This diagram demonstrates how the LM7824 maintains stable output voltage when the load changes. A transistor and load resistor are used to simulate different load conditions. When the load current increases or decreases, the internal regulation circuitry of the LM7824 adjusts the conduction of its internal pass transistor to keep the output voltage constant. The small capacitor and resistor network helps measure and stabilize the response during fast load changes. This circuit helps test how well the regulator keeps the output voltage stable under varying loads.

Ripple Rejection Circuit

This circuit illustrates how the LM7824 reduces ripple voltage from the input power source. The input supply contains ripple, represented by the AC signal source and large capacitor. The 0.33µF capacitor at the input helps filter high-frequency noise, while the regulator internally suppresses ripple through its control circuitry. The load resistor represents the device powered by the regulator. As a result, even if the input voltage contains ripple, the LM7824 produces a clean and stable 24V output, making it useful in regulated DC power supplies.