78L05 5V 100mA Voltage Regulator – TO-92 Package

The 78L05 is a compact 5V linear voltage regulator designed to provide a stable regulated 5V output for low-power electronic circuits. Housed in a small TO-92 through-hole package, it is particularly useful where a circuit requires a regulated 5V supply but does not need the higher current capability of larger voltage regulators.
With an output current of up to approximately 100mA, the 78L05 is suitable for powering low-current electronic circuits, sensors, logic circuits, small microcontroller systems, and other 5V devices. It can accept a higher DC input voltage and regulate it down to approximately 5V, provided the device is operated within its voltage, current, power-dissipation, and temperature limits.
Its small size makes the 78L05 particularly useful for electronic kits, compact PCBs, prototypes, repairs, and classroom electronics projects where students can investigate voltage regulation and regulated power supplies.

Key Features

• Fixed 5V regulated output
• Up to approximately 100mA output current
• Compact TO-92 package
• Linear voltage regulation
• Suitable for low-power 5V circuits
• Internal current limiting and thermal protection typical of the 78L05 family
• Low component count required
• Through-hole mounting
• Suitable for PCB and breadboard projects
• Useful for microcontrollers, sensors, and logic circuits

What’s Included

• 1 × 78L05 5V 100mA Voltage Regulator – TO-92

What Does a Voltage Regulator Do?

Electronic circuits often require a stable supply voltage to operate correctly. A voltage regulator takes a higher DC input voltage and maintains a substantially constant output voltage despite reasonable changes in input voltage or circuit load.
The 78L05 provides a fixed output of approximately 5V, making it useful for circuits containing components designed to operate from a regulated 5V supply.
For example, a circuit powered from a higher-voltage DC source can use a 78L05 to create a regulated 5V supply for low-current electronics.

Linear Voltage Regulation

The 78L05 is a linear regulator. Unlike a switching regulator, it reduces the voltage by dissipating the excess electrical power as heat.
The greater the difference between the input and output voltage, and the greater the load current, the more heat the regulator must dissipate.
For this reason, the 100mA rating should be treated as a maximum capability under suitable operating conditions, rather than assuming 100mA can always be drawn regardless of input voltage and temperature.

Input Voltage

A 78L05 requires its input voltage to remain sufficiently above the regulated 5V output for correct regulation. Around 7V or higher is commonly used as a practical minimum, although the exact dropout requirement depends on the particular manufacturer’s device and operating conditions.
Some 78L05 variants permit input voltages up to around 30–35V, but the exact maximum input voltage should always be checked against the datasheet for the supplied manufacturer and part number.
Using a very high input voltage with a significant load current can also cause excessive power dissipation and heating even when the voltage remains within the device’s absolute maximum rating.

Common Applications

• 5V regulated power supplies
• Microcontroller circuits
• Sensor circuits
• Logic circuits
• Electronic kits
• Audio circuits
• Indicator circuits
• Battery-powered electronics
• PCB projects
• Prototyping and repairs

Classroom Use / Learning Outcomes

Students can use the 78L05 to:
• Understand voltage regulation
• Compare regulated and unregulated power supplies
• Measure input and output voltage
• Learn why electronic circuits require stable supply voltages
• Investigate current and power consumption
• Understand power dissipation in linear regulators
• Build simple regulated power supplies
• Develop breadboard and PCB construction skills
• Use a multimeter to test power-supply circuits

Teacher Benefits

• Useful component for teaching regulated power supplies
• Compact through-hole package suitable for student projects
• Provides a practical introduction to linear regulation
• Suitable for breadboard and PCB activities
• Can be incorporated into electronic kits and control circuits
• Useful for demonstrating voltage measurement and troubleshooting

Important Pinout Information

The 78L05 is commonly supplied in a TO-92 package, but pin assignments should not be assumed solely from the package shape. Always check the datasheet for the exact manufacturer and part number supplied before PCB design or connection, as pin configurations can vary between devices and manufacturers.

Perfect For

• Electronic kits
• 5V power supplies
• Microcontroller projects
• Sensor circuits
• Logic circuits
• Breadboard experiments
• PCB assembly
• STEM electronics
• Repairs and prototyping
• Classroom electronics