Power Supply Circuits Primer & Tutorial Includes:
Power supply electronics overview Linear power supply Switch mode power supply Over-voltage protection PSU specs Digital Power Power management bus: PMbus
The 7805, 7812, and other variants in the 78** series of regulator ICs have remained very popular for many years. These regulator ICs offer very acceptable levels of performance for most applications and in addition to this they are very cheap and easy to use. Having only three terminals, i.e. input, output and ground, they require no external components for their basic operation.
Although the mainstay components are the 7805 and 7812 themselves, other variants supply other voltages, the last two digits indicating the voltage output. In addition to this there are low power variants 78L** and high power variants 78H**.
The 7805 and 7812 are positive voltage regulators supplying a positive voltage. However there is an equivalent series of negative voltage regulators - the 79** series including the 7905 and 7912. These are virtually the same as the 7805, 7812 and the remaining variants in the 78** series, but they provide a negative instead of a positive output.
By Ian Poole
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