78xx (sometimes L78xx LM78xx MC78xx?) is a family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is commonly used in electronic circuits requiring a regulated power supply due to their ease-of-use and low cost.
There are common configurations for 78xx ICs including 7805 (5 V) 7806 (6 V) 7808 (8 V) 7809 (9 V) 7810 (10 V) 7812 (12 V) 7815 (15 V) 7818 (18 V) and 7824 (24 V) versions. The 7805 is the most common as its regulated 5-volt supply provides a convenient power source for most TTL components.
Less common are lower-power versions such as the LM78Mxx series (500 mA) and LM78Lxx series (100 mA) from National Semiconductor. Some devices provide slightly different voltages than usual such as the LM78L62 (6.2 volts) and LM78L82 (8.2 volts) as well as the STMicroelectronics L78L33ACZ (3.3 volts).