How to Use 7808: Examples, Pinouts, and Specs

The 7808 is a fixed-output, positive-voltage linear regulator that is designed to deliver a stable 8V DC output. It is a member of the 78xx series of voltage regulators, which are widely used in electronic circuits for providing a constant voltage supply to various components such as microcontrollers, sensors, and other integrated circuits. The 7808 is particularly useful in applications where a reliable and consistent 8V power source is required.

• Power supplies for electronic devices and circuits
• Battery chargers
• Voltage step-down circuits from higher voltage sources
• Motor control circuits
• Microcontroller-based systems

• Output Voltage: +8V
• Input Voltage (recommended): 10.5V to 20V
• Input Voltage (maximum): 35V
• Output Current (maximum): 1A (with adequate heat sinking)
• Quiescent Current: 5mA (typical)
• Output Voltage Tolerance: ±5%
• Thermal Overload Protection: Yes
• Short Circuit Protection: Yes
• Package Type: TO-220 (commonly)

1. Connect the unregulated input voltage (10.5V to 20V) to the Input pin (Pin 1).
2. Connect the Ground pin (Pin 2) to the common ground of your circuit.
3. The regulated 8V output can be drawn from the Output pin (Pin 3).

• Always use a capacitor on the input and output to minimize voltage fluctuations:
  • A typical value for the input capacitor (Ci) is 0.33µF.
  • A typical value for the output capacitor (Co) is 0.1µF.
• Ensure the input voltage is always at least 2.5V higher than the output voltage to maintain regulation.
• Do not exceed the maximum input voltage of 35V to prevent damage.
• The maximum output current is 1A; however, ensure proper heat sinking if the regulator is to deliver currents near this maximum rating.
• Avoid placing the regulator in environments that exceed its temperature ratings.

• Voltage Drop: If the output voltage is lower than expected, check the input voltage and ensure it is at least 2.5V higher than the output.
• Overheating: If the regulator is overheating, consider adding a heat sink or reducing the load current.
• No Output: Ensure that the input voltage is within the specified range and that the capacitors are correctly installed.

• Verify the input and output connections are correct.
• Check for any short circuits in your load that could be causing excessive current draw.
• Ensure that the capacitors are of the correct value and are properly connected.
• If the regulator does not start, temporarily disconnect the load to see if the regulator outputs the correct voltage without it.

Q: Can I use the 7808 without capacitors? A: It is not recommended to use the 7808 without capacitors as they help to stabilize the output voltage and reduce noise.

Q: What is the maximum current the 7808 can supply? A: The 7808 can supply up to 1A of current, but adequate heat sinking is necessary to maintain thermal performance.

Q: Can I connect loads that require more than 1A to the 7808? A: No, you should not exceed the maximum current rating of 1A. For higher currents, consider using a different regulator or parallel connection with proper current sharing.

Q: How can I increase the output current capability? A: To increase the output current, you may need to use an external pass transistor or a different regulator designed for higher currents.

Q: Is the 7808 compatible with Arduino UNO? A: Yes, the 7808 can be used to power an Arduino UNO or similar devices that require an 8V input, as long as the current requirements do not exceed 1A.

If you have any further questions or require additional assistance, please consult the datasheet for the 7808 voltage regulator or contact technical support.