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Startseite > Other > LM7809 Voltage Regulator: Pinout, Circuit, Datasheet, and Uses

LM7809 Voltage Regulator: Pinout, Circuit, Datasheet, and Uses

Updatezeit: 2023-11-29 13:51:22


Providing precisely the appropriate voltage represents a pivotal requirement in every electronic setup. Consequently, an optimal voltage regulator must effectively transform the incoming voltage into the intended output. How can we guarantee a steady voltage supply to external elements? The answer lies in a linear voltage regulator. In this article, we'll explore the functionality of an LM7809 voltage regulator, including its pinout, circuit, specifications, working, datasheet, and more details. Therefore, delve into this piece for a comprehensive examination of voltage and output current.

What is LM7809?

The LM7809 serves as a dedicated positive voltage regulator integrated circuit, engineered for a wide spectrum of applications. This IC ensures a consistent 9V output, with a current range spanning from 1A to 1.5A. To maintain a fixed and dependable 9V output at 1.5 amperes, the input voltage should be set at 11V, requiring a 2A input.

Should the input voltage dip below 11V, the IC will fail to provide a steady 9V, as it mandates a 2V surplus over the specified output voltage to deliver a reliable result. The maximum allowable input voltage stands at 35V DC. It is imperative to employ an adequate heatsink in conjunction with the IC since any voltage differential will be converted into heat within the IC.


Furthermore, the IC incorporates several inherent features, including overheat shutdown and short-circuit protection, bolstering its reliability for deployment in a multitude of commercial applications and educational electronic projects.

LM7809 Pinout


Pinout Configuration

Pin No.Pin NameDescription
1Input (V+)Unregulated Input Voltage
2GroundConnected to Ground
3Output (Vo)Outputs Regulated +9V

LM7809 Features

  • Current Output Range: 1A to 1.5A

  • Cost-Effective

  • Suitable for Commercial Applications

  • Ensures a Steady and Consistent 9V Output

  • Capable of Handling a Maximum Input Voltage of 35V DC

  • Extremely Low Sleep Mode or Standby Current Consumption: Just 8mA

  • Minimum Required Input Voltage: 11V

  • Maximum Allowed Input Voltage: 35V

  • Impressive PSRR (Power Supply Rejection Ratio) / Ripple Rejection: 55 dB

  • The IC Maintains a Fixed Output Voltage of 9V with a Tolerance of +/- 4%, featuring a Drop-Out Voltage (VI – VO) of 2.0V.

  • Output Type: Fixed

  • Equipped with Internal Thermal Overload Protection and Short Circuit Current Limiting

  • Maximum Junction Temperature: 125 degrees Celsius

  • Available in TO-220, TO-3, and KTE Packages

LM7809 Specifications

Nominal Supply Current5mA
Quiescent Current8mA
Output ConfigurationPositive
Voltage Dropout (Max)2V @ 1A Typ
Terminal PositionSINGLE
Protection FeaturesOver Temperature, Short Circuit
Dropout Voltage2V
Dropout Voltage1-Nom2V
Output Voltage Accuracy4 %

Power Dissipation of a 7809 Voltage Regulator


LM7809 Typical Performance Characteristics

Why opt for the 7809 voltage regulator over traditional DC-DC converters? While both serve a common purpose, the 7809 voltage regulator proves more effective. Notably, it generates fewer ripples in its output compared to DC-DC converters.

However, the 7809 voltage regulator does have the drawback of dissipating more heat.

A key component to consider is the presence of a series pass transistor at the output. This component plays a crucial role in reducing excessive voltage within the circuit. It's worth noting that the power dissipation can be calculated using the formula: Power Dissipation = (Input Voltage - Output Voltage) x Output Current.

To illustrate, let's work through an example:

Example: Take a 7809 voltage regulator with an input voltage of 12V and a current of 1A.

Solution: Given that the output voltage remains steady at 9V, the power dissipation in the circuit equals (12V - 9V) x 1A, which totals 3 watts.

Typically, a voltage converter can handle a maximum of 1.25 watts without requiring a heat sink. Therefore, in our scenario, the inclusion of a heat sink becomes necessary.

9V Power Supply Using 7809 Voltage Regulator

The 7809 stands as a commonly employed linear regulator. Its input voltage can span from 11 to 35VDC, and it consistently delivers a fixed 9V with a continuous current of over 1A, and a surge current capability of up to 2.2A.

For basic functionality, no additional components are necessary. Simply connect the input voltage and ground, and you'll have a stable 9V available at the output.

However, suppose you intend to use it at a considerable distance (greater than 10 inches) from the power source supplying the input voltage. In that case, it's advisable to include a .33uF or larger input filter capacitor. Ideally, this capacitor should possess a low ESR (Equivalent Series Resistance), such as a Tantalum or Mylar capacitor, although small electrolytic capacitors generally suffice. Additionally, you have the option to add an output capacitor of 0.1uF or larger to enhance the output's transient response, as depicted below.


7809 9V Regulator with Bypass Caps

L7809 as +9V Voltage Regulator

Here is a typical application circuit for the 7809 IC. It requires just two capacitors, one with a value of 0.33uF and the other with a value of 0.1uF, to operate effectively. The 0.33uF input capacitor, which is a ceramic capacitor, addresses input inductance issues, while the 0.1uF output capacitor, also ceramic, enhances circuit stability. It's important to position these capacitors close to the IC terminals for optimal performance. Additionally, it's advisable to use ceramic capacitors, as they offer faster response compared to electrolytic capacitors.


LM7809 Equivalent

LM7806, LM7824, LM7815, LM7812, LM317, LM7905, LM7912 can equivalent to LM7809.

LM7809 Applications

  • Providing a steady +9V output to power microcontrollers and sensors

  • Voltage step-down applications

  • Power supply systems

  • Motor driver circuits

  • Battery charger designs

  • Solar power systems

  • Microcontroller power sources

  • Adjustable output regulators

  • Current limits in specific applications

  • Regulated dual power supplies

  • Output polarity reversal protection circuits

LM7809 CAD Model


LM7809 symbol.png


LM7809 footprint.png

3D Model

LM7809 3d model.png

LM7809 2D Model

LM7809 Package.png

LM7809 Datasheet

Download LM7809 Datasheet PDF.


As you've observed, a 7809 voltage converter operates with simplicity, yet it effectively maintains a steady 9V output voltage. The LM7809 voltage regulator is a fundamental component for voltage regulation in electronic circuits. It offers stability, reliability, and versatility, making it an essential part of countless applications in the world of electronics.

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  • What is the function of LM7809?
  • The L7809 voltage regulator is capable of supplying a 9V positive output voltage and offers localized on-card regulation, effectively mitigating the distribution challenges linked to single-point regulation.

  • What is the maximum current output of LM7809?
  • The 7809 is a linear regulator with a fixed output voltage of 9V, capable of providing a current of up to 1A. It operates within an input voltage range of 11 to 35V.

  • How to use LM7809?
  • LM7809 is an integrated three-terminal voltage regulator module. It necessitates a DC input voltage within the range of 12 to 25V and should be accompanied by an input filter capacitor. Due to the substantial voltage differential, the use of a heat sink is imperative.

  • How should the voltage regulator be wired to work properly?
  • For optimal regulation and the best output performance, it's important to provide the voltage regulator with a clean and stable DC input signal. This allows the regulator to effectively reduce the voltage to its specified level.

  • How to build a voltage regulator circuit?
  • The circuit consists of a 7805 linear voltage regulator in conjunction with capacitors.

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