7805

7805 is a fixed positive voltage regulator in the 78xx family that provides a regulated +5-volt output from a higher input voltage. It is widely used to supply microcontrollers, digital logic, and other low-power circuits in consumer electronics and hobby projects.

Typical specifications describe an input voltage range up to about 30–35 V, with a maximum continuous output current around 1 A (depending on package and heat sinking). The dropout voltage is typically about 2 V at full load, meaning the input must be a few volts higher than 5 V to maintain regulation. The device includes internal current limiting and thermal shutdown to protect itself under fault or overheating conditions.

The standard package form is a three-terminal device, often in a TO-220 or surface-mount package. The three terminals are input, ground, and output. Pinout can vary by package and manufacturer, so the datasheet should be consulted for the exact arrangement. The tab is typically connected to one of the pins (commonly ground or input), depending on the variant and package.

Applications focus on providing a stable 5 V rail for digital logic and small systems, frequently in bench power supplies or as part of a larger regulated power supply. Proper decoupling is recommended: a small capacitor (about 0.33 µF) at the input and a 0.1 µF capacitor at the output for stability, with larger electrolytics (for example 10–100 µF) to improve ripple rejection and transient response when needed.

Limitations include heat dissipation from (Vin − Vout) × I, which can require adequate heatsinking or a switch-mode alternative for higher loads or larger voltage drops. The 7805 has several relatives in the 78xx family, including different output voltages and low-dropout variants.