Why is LM7805 output 4.94 volt only instead of 5 volt?

Thread Starter

dante_clericuzzio

Joined Mar 28, 2016
213
Hi i would like to ask opinion from any experience/experts here...I am testing the LM7805 that i just purchased and using 9.6 volt battery...based on the datasheet it should produce at least 5 volt or a little more like 5.2 volts..However the output i see is only 4.94 volt my questions is

Is the LM7805 defect or am i missing something here?

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tracecom

Joined Apr 16, 2010
3,944
Electronic components have a tolerance. The LM series of voltage regulators are not precise devices, and 4.94 V is within the guaranteed range. Check the datasheet for its exact tolerances. There are other regulators that are more precise and there are ways to add some components to fine tune the output of the LM7805; again, this is described in the datasheet.
 

Thread Starter

dante_clericuzzio

Joined Mar 28, 2016
213
4.94V is not bad for 7805.
If you need precision, consider using LM317 (or LM338 if you need high cirrent)
Thank you for the suggestion actually i am trying to find a circuit diagram that uses 9 volt to output 5 volt and 1.5 amp to 2 amp current. But i couldn't find any....do you have suggestion or this is not possible to use 9 volt battery?
 

dl324

Joined Mar 30, 2015
10,708
Assuming alkaline battery chemistry, you'd be lucky to get 5 or 10 minutes before the regulator dropped out.
RAYOVAC 9V Alkaline Battery:
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bushrat

Joined Nov 29, 2014
209
LM338 is your best choice, it has max 5A output. (provided you have sufficient source to power it up)
LM317 only has 1.5 A and you need heatsink.
7805 can only provide 1A and you need heatsink if you are going over 0.5A
Driving 2A from 9V battery will last you for few minutes before voltage starts to drop.
 
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