781C

781C is a designation used in electronics to refer to a fixed-output positive voltage regulator in the 78xx family. Like other 78xx regulators, it is designed to provide a stable DC output from a higher unregulated input and is commonly used in power supplies for consumer electronics and microcontroller projects. The exact output voltage associated with "781C" varies by manufacturer and revision; while many catalog entries approximate 5 volts, the precise value should be verified in the datasheet.

Regulators of this type maintain a constant output by controlling a pass transistor. The input voltage must exceed the desired output by a dropout margin, typically around 2 V at moderate loads. Current ratings for standard 781C devices are often in the range of several hundred milliamps up to about 1 A or more with adequate heat sinking. Output voltage tolerance varies with temperature and manufacturer specifications.

Packages commonly include TO-220 and surface-mount variants. These regulators typically include short-circuit protection and thermal shutdown; additional protections and features vary by model. External capacitors on the input and output are usually recommended to improve stability and transient response.

Applications include linear power supplies for 5-volt logic, embedded systems, and educational circuits. The 781C designation is part of the broader 78xx family, with origins in the 1970s and production by many manufacturers such as National Semiconductor (now part of TI), STMicroelectronics, and Fairchild. When sourcing a 781C, users should consult the specific datasheet for voltage, current rating, packaging, and temperature range.