Sunday 16 June 2019

7812 minimum input voltage?



On the datasheet it doesn't mention an input voltage. Must the input voltage be higher than the output voltage or does it increase to 12 V if I input 8 V for example?


If so, what is the current like that it outputs?



Answer



A 7812 is a linear regulator, and does not step up the input voltage if the input is below the output (for that you need a DC-DC boost regulator). The input voltage must be above the output. All linear regulators have a minimum dropout voltage, or difference.


The 7812 is not a LDO (low-dropout regulator), as the typical dropout voltage is around 2 volts. (An LDO might have a dropout voltage of 0.7 volts).


On page 6 of the datasheet, the maximum dropout voltage Vd is listed as 2.5 volts, meaning you need a minimum of 14.5 volts input to the device to guarantee an output of 12 volts..


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