78L05 Voltage Regulator Pinout, Parameters, and Circuit Diagram

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78L05 Voltage Regulator

In general, voltage regulators are very common in various electronic circuits because they provide a fixed output voltage for different input voltages. The 78L05 regulator in the L78LX family uses thermal shutdown and internal current limit, making it essentially indestructible. Once adequate heatsinking is provided for this regulator, it will deliver up to 100A of output current.

These types of voltage regulators are fixed in a wide range of applications. In addition, the 78L0 can also be used to build voltage regulators with large currents through power transfer elements.

About the 78L05 Voltage Regulator

In a 78L05 regulator, the first two numbers such as “78” are positive voltages, 05 is the output voltage produced by this C, such as 5V, and the letter “L” between 78 and 05 is low current, such as 0.1A. This voltage regulator is used in most electronics projects.

The output current of this voltage regulator is as high as 100A, but the heat loss is very large. Hence, it is recommended to use a heatsink for electronic projects as it uses more current. Another more popular voltage regulator is the 7805, but it is larger and has a high current rating of 1A. Therefore, if you are looking for a regulator in a smaller package, then the 78L05 regulator is more suitable.

Pin Configuration

The pin configuration of the 78L05 voltage regulator includes three pins, as shown in the following figure:

78L05 Pinout
78L05 Pinout
  • Pin1 (Output (Vo)): This pin provides stable +5V.
  • Pin2 (ground/GND): This l pin is connected to GND.
  • Pin3(Input(V+)): This is a fixed input voltage.


  • Output Voltage Tolerance +/-5% Over Temperature
  • O/P transistor safe area protection
  • Thermal overload protection
  • Full military temperature range
  • Short circuit protection
  • No additional components required


  • Input voltage (maximum value) is 30V
  • The output current is 100mA
  • The voltage regulator positive voltage is 5V
  • Working current is 5mA
  • Available packages are S0-8, S0T-89 and T0-92
  • With short-circuit current limiting and internal thermal overload protection

How to Test 78L05 Voltage Regulator?

We can test the 78L05 regulator by removing the positive probe from the i/p pin and placing it on the o/p pin, the negative probe can be placed on the GND pin. Of course, since the voltage associated with this regulator is 05, the output voltage must be 5V.

Circuit Diagram of 78L05 Voltage Regulator

The 78L05 voltage regulator application circuit is shown in the figure below. This circuit is used to regulate the 12V input voltage to 5V output voltage. In this circuit, a 78L05 voltage regulator plays a key role.
The 78L05 voltage regulator consists of three terminals namely i/p, o/p and GND. So it is very simple to use by connecting the input pin to WVi and the GND pin to system GND.

An Example of 78L05 Voltage Regulator Circuit Diagram
An Example of 78L05 Voltage Regulator Circuit Diagram

The input voltage (say 12V) is regulated to 5V with the help of a voltage regulator 1C. So this output voltage is very useful for activating small loads with a rated current below 100A.
The maximum current supplied by the 78L05 regulator is 100mA.

In the above circuit, capacitors such as C1 and C are connected to the input and output terminals. The main function of these capacitors is to filter the noise of the input voltage. Of course, it is not mandatory to use exact capacitor values, but a “C1″ value of 10u” and a “C2″ value of 1u” would be an option. Once the temperature exceeds the junction temperature, these voltage regulators can limit the current and protect the .

If you connect this circuit to a high current load, it may heat up and eventually stop working. So using a suitable voltage regulator is a perfect choice. In addition to being used as a voltage regulator, it can also be used as a short circuit protector, variable voltage regulator, current regulator, boost circuit.

Application of 78L05 Voltage Regulator

The 78L05 voltage regulator is a three-terminal fixed voltage regulator, so it is used in many applications. The 78L05 regulator features thermal shutdown and excellent internal current, which will enable its use in overload applications. Once this regulator is used to change the usual susceptibility diode, its 0/p impedance is effectively enhanced, however, the bias current is greatly reduced.

Like single-point voltage regulators that need to limit noise and solve distribution problems, the 78L05 can also be used with other power delivery devices to form a high-current regulated voltage supply, such as up to 100mA regulated output current.

The application of 78L05 voltage regulator mainly has the following points:

  • Current Limiter Variable Output Voltage
  • LED lighting
  • Portable instrument
  • Microcontroller application
  • Small load can supply power below 100mA
  • Different circuits such as power supplies, battery chargers, output boosters, buck

78L05 Equivalent and Alternative

Alternative 78L05 regulator models are the LM7809, LM7806, LM317, LM7912, XC6206P332MR, LM7905, LM7812, and LM117V33.

Equivalent 78L05 regulator models are the AMS7111 and LM7805.


This post introduce the basic content related to the 78L05 voltage regulator, mainly including its pin configuration, specifications, characteristics and application circuits. Its application ranges from DVD-ROM, CD-ROM, sound card, computer motherboard, to linear voltage regulator, controller and other equipment.


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Aidan Taylor
Aidan Taylor

I am Aidan Taylor and I have over 10 years of experience in the field of PCB Reverse Engineering, PCB design and IC Unlock.

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