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

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 Name	Description
1	Input (V+)	Unregulated Input Voltage
2	Ground	Connected to Ground
3	Output (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

Type	Parameter
Nominal Supply Current	5mA
Quiescent Current	8mA
Output Configuration	Positive
Voltage Dropout (Max)	2V @ 1A Typ
Terminal Position	SINGLE
Protection Features	Over Temperature, Short Circuit
Dropout Voltage	2V
Dropout Voltage1-Nom	2V
Output Voltage Accuracy	4 %

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

Symbol

Footprint

3D Model

LM7809 2D Model

LM7809 Datasheet

Download LM7809 Datasheet PDF.

Conclusion

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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