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Home > Other > 78L05 Voltage Regulator: Pinout, Equivalent, Uses & Datasheet

78L05 Voltage Regulator: Pinout, Equivalent, Uses & Datasheet

Update Time: 2023-12-28 13:44:54


Typically, voltage regulators play a prevalent role in diverse electronic circuits by furnishing a consistent output voltage despite variations in input voltage. The 78L05, a member of the L78Lxx series, employs thermal shutdown and internal current limiting mechanisms, rendering it impervious to damage. When equipped with an adequate heat sink, this regulator can efficiently deliver an output current of up to 100 mA.

These specific voltage regulators find application across a broad spectrum of uses. Moreover, they can be integrated via power pass elements to construct high-current voltage regulators. In this article, we'llll delve into the 78L05 voltage regulator, exploring its pinout, circuit, features, uses, datasheet and more details.

What is a 78L05 Voltage Regulator?

The 78L05 is a 5V fixed 3-terminal voltage regulator, capably delivering up to 100mA of output current, boasting internal limiting and thermal shutdown features for resilience against overloads. In the terminology of the 78L05 voltage regulator, the initial two digits, such as '78', denote a positive voltage, while '05' signifies the output voltage of 5V. The intervening letter 'L' designates a low current, around 0.1A.


The 78L05 provides local, on-card regulation, obviating issues associated with single-point regulation distribution. It incorporates current limiting to cap the peak output current at a safe level, along with safe area protection for the output transistors to constrain internal power dissipation. The thermal shutdown circuit intervenes if internal power dissipation exceeds the capacity of the provided heat sinking, preventing the IC from overheating.

When employed as a substitute for a Zener diode/resistor combination, the 78L05 enhances output impedance significantly, lowers quiescent current, and reduces noise by two orders of magnitude. Furthermore, the 78L05 can be effectively utilized with power-pass elements to construct high-current voltage regulators.

78L05 Pinout

Displayed below is the pin arrangement of the 78L05 voltage regulator. This regulator is equipped with three pins, and each pin and its respective function are elucidated in the following discussion.

78L05 Pinout.png

Pin Configuration

Pin No.Pin NameDescription
1Output (Vo)Outputs Regulated +5V
2Ground (Gnd)Connected to Ground
3Input (V+)Unregulated Input Voltage 

Features & Specifications

A 5V fixed 3-terminal positive voltage regulator capable of delivering an output current of up to 100mA is detailed below:

  • Maximum input voltage: 30V

  • Operating current (IQ): 5mA

  • Maximum output current: 150mA

  • Power dissipation: 0.5W

  • Operating temperature range: -40 to +85 °C

  • Features internal thermal overload and short-circuit current limiting protection.

  • Packaging options include TO-92, SO-8, and SOT-89.

78L05 Alternative Regulators

Alternative voltage regulators for 78L05 include LM7806, LM7809, LM7812, LM317, LM7905, LM7912, LM117V33 and XC6206P332MR.

78L05 Equivalent Voltage Regulators

AMS7111 and LM7805 can be equivalent to 78L05.

78L05 Negative Voltage Complement


Where to use 78L05

Voltage regulators play a ubiquitous role in electronic circuits, ensuring a consistent output voltage despite fluctuations in input voltage. In our context, the 78L05 IC stands out as an iconic regulator with widespread applications in numerous projects. The terminology "78L05" conveys dual information: "78" indicates it's a positive voltage regulator, and "05" denotes a 5V output. Therefore, our 7805 will yield a +5V output.

While the IC supports an output current of up to 100mA, it encounters significant heat dissipation, necessitating a heat sink for projects with higher current consumption. For instance, if the input voltage is 12V and the consumption is 50mA, the heat dissipation can be calculated as (12-5) * (50*10^-3) = 0.35W, which will be dissipated as heat.

Another noteworthy voltage regulator is the 7805, which is larger but boasts a higher current rating of approximately 1A. If you seek a compact voltage regulator with a smaller current rating in a TO-92 package, the 78L05 IC emerges as a fitting choice.

How to use 78L05

The 78L05 is a three-terminal voltage regulator featuring Input, Output, and ground terminals, as illustrated in the 78L05 pinout diagram. Utilizing this IC is straightforward—connect the input to the regulated input voltage and the ground pin to the system ground.

In the presented circuit, a 12V input voltage is regulated to 5V using the 78L05. The 5V output can power small loads, such as LEDs, rated for less than 100mA, given the IC's maximum current supply of up to 100mA.


Note the inclusion of capacitors C1 and C2 at the input and output. These capacitors serve to filter any noise coupled with the input voltage. While the exact capacitor values are not mandatory, opting for 10uF for C1 and 1uF for C2 is ideal.

These regulators possess current limiting and temperature protection capabilities. Connecting high current loads may cause the IC to heat rapidly and eventually shut down. In such cases, opting for a high current regulator like the 7805 is advisable.

Beyond its role as a voltage regulator, the 78L05 can serve as a current regulator, short-circuit protector, booster circuit, and even a variable voltage regulator. Refer to page 27/45 in the provided 78L05 datasheet for circuits about these applications.

78L05 Schematic Diagram

78L05 Schematic Diagram.png

78L05 Test Circuit

78L05 Test Circuit.png

78L05 Layout

78L05 Layout.png

Circuit Explanation

Incorporate the regulator into the circuit design with two ceramic capacitors strategically placed at both ends. These capacitors, a 10uF input capacitor and a 1uF output capacitor, serve the crucial role of filtering noise associated with the input voltage. Beyond their differing values, the input capacitor addresses input inductance concerns, while the output capacitor enhances circuit stability.

Notably, this widely used voltage regulator boasts a temperature-sensitive feature that engages when the circuit temperature surpasses the junction temperature. This particular feature provides an added layer of circuit protection.

Advantages of 78L05

The 78L05 voltage regulator offers several advantages:

  • Output voltage tolerance of +/-5% across the temperature range.

  • Safe area protection for the output transistor.

  • Thermal overload protection.

  • Full coverage of the military temperature range.

  • Safeguarding against short circuits.

  • Requires no additional components.

What is the Difference between 78L05 and 7805?


The LM7805 is a voltage regulator producing a +5 volts output with a capacity of 1A. Similar to many regulators available, it conforms to the standard three-pin IC configuration: an input pin for receiving incoming DC voltage, a ground pin for establishing the regulator's ground reference, and an output pin that furnishes the positive 5 volts.

On the other hand, the LM78L05 belongs to the LM78Lxx series of positive voltage regulators, delivering a steady output of 5V with a capacity of 100mA DC.

Part Numbers

The 7805 serves as the original manufacturer part number, where "78" designates positive voltage, contrasting with "79" indicating negative voltage, and "05" specifying a positive 5V output.

The letters between "78" and "05" denote the current rating. Specifically, "78L05" signifies a low current at 0.1A, "78M05" indicates a medium current at 0.5A, "78S05" represents a high current at 2A, and "78T05" corresponds to an even higher current, potentially reaching 3A. Meanwhile, the "7805" maintains a typical current of 1A.

The final two digits convey various output voltages. For instance, "7805" corresponds to a 5V output, "7806" signifies a 6V output, "7808" designates an 8V output, and so forth.


In many instances, one may substitute the 78L05 with the 7805; however, notable distinctions exist between them. Although their functions align, their pin configurations differ. For the 7805, pins 1, 2, and 3 correspond to input, ground, and output, while for the 78L05, the order is reversed, with pins 1, 2, and 3 representing output, ground, and input. Additionally, they are commonly available in distinct packages—TO-220 for the 7805 and TO-92 for the 78L05.

While both regulators share the same output voltage, their output currents vary, with the 78L05 at 0.1A and the 7805 at 1A. Physically, the 78L05 is smaller than the 7805, allowing for less power dissipation and a lower current rating.

78L05 Applications

  • A regulator providing a steady +5V output for powering loads below 100mA,

  • An adaptable output regulator,

  • Inclusion of a current limiter for specific applications,

  • Incorporation of an output polarity-reversal-protection circuit,

  • Integration of an output booster circuit,

  • Capability for variable output voltage,

  • Suitability for LED lighting applications,

  • Applicability in portable instruments,

  • Relevance to microcontroller applications,

  • Versatility across various circuits includes power supply, battery charger, output booster, and step-down voltage circuits.

78L05 Application Circuits

78L05 High Output Current Short-Circuit Protected

78L05 High Output Current Short-Circuit Protected.png

78L05 Output Boost Circuit

78L05 Output Boost Circuit.png

78L05 Current Regulator

78L05 Current Regulator.png

78L05 Adjustable Output Regulator

78L05 Adjustable Output Regulator.png

78L05 ±15-V, 100-mA Dual Power Supply Circuit

78L05 ±15-V 100-mA Dual Power Supply Circuit.png

78L05 Variable Output Regulator Circuit (0.5 V to 18 V)

78L05 Variable Output Regulator Circuit (0.5 V to 18 V).png

78L05 Datasheet

Download 78L05 Datasheet PDF.


The 78L05 voltage regulator is a versatile and reliable component for applications requiring a regulated +5V supply. Whether powering microcontrollers, sensors, or educational projects, the 78L05's straightforward design and stable output make it a popular choice in electronic circuits. When implementing this regulator, ensure adherence to the specified input voltage limits, consider decoupling capacitors and be mindful of its limitations in terms of output current.

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  • What does a 78L05 do?
  • The 78L05 is a 3-terminal voltage regulator with a fixed output of 5V. It can provide a maximum output current of 100mA and includes internal limiting and thermal shutdown features to ensure overload protection.

  • What is the current limit of 78L05?
  • 100mA.

  • Is 78L05 a transistor?
  • The 78L05 is a built-in +5V voltage regulator, not a transistor.

  • What is the voltage of 78L05?
  • 5V DC.

  • How do you safely long-run 78L05 in a circuit?
  • To ensure prolonged functionality of the LM78L05 voltage regulator, it is recommended to consistently operate it at 20% below its maximum specified ratings. The IC's enduring load capacity is 100mA DC, with a safety threshold of not exceeding 80mA DC. It is imperative not to subject the IC to an input voltage surpassing 35V DC; for safety considerations, the input voltage should be maintained within the range of 28 to 30V DC. Operate the IC within a temperature spectrum from 0 degrees Celsius to 85 degrees Celsius. The storage temperature parameters range from -65 degrees Celsius to +150 degrees Celsius.

  • How do you test 78L05?
  • Transfer the positive probe from the input to the output pin, leaving the negative probe connected to the ground pin. Ideally, the displayed output voltage should read 5 volts by the "05" designation 78L05.

  • When should you use a voltage regulator?
  • Voltage regulators serve the purpose of preserving and steadying voltage levels. These regulators are integral components in many electronic devices, effectively reducing and regulating voltage outputs from high-voltage sources while managing surplus energy through heat dissipation.

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