What is the difference between adjustable regulators and generic ones like 78xx ?

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hello friends

what is difference between adjustable regulators and generic ones like 78xx ?
is it meaning that we can set the output of adjustable regulators on any desirable voltage? how?
 

Re: adjustable regulator

yes the adjustable regulators like LM317 are adjustable regulators where the output voltage can be adjusted... but not with the LMxx series ....
 

Re: adjustable regulator

You can easily adjust a fixed voltage regulator too but the output voltage will be at least the rated voltage for that regulator,
for example a 7812 can only be adjusted to an output over 12v.
Usually this is not the way that a fixed regulator is used.
Check page 23-24 of the datasheet for examples https://www.fairchildsemi.com/ds/LM/LM7805.pdf

An adjustable voltage regulator will have a very low minimum voltage (1.2v for LM317) and it can
only be used with external components that adjust the output voltage

In both cases the output voltage can be calculated using the datasheet formulas.

Alex
 
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Re: adjustable regulator

yes ,generally we can set the output of adjustable regulators by a variable resistor.like LM337 or LM337,they are easily to be used,you can look up their datesheets for more information.
 

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