I have 7805 regulator. I know its output is 5v
What is its maximum input?
any comments will help. thank you!

 

It is in the datasheet.

 

The 7805 data sheet (just Google "7805" to find one) will give you that info, under Absolute Maximum Ratings. For the Fairchild 7805 (the first one that comes up on Google), its 35 volts.

 

The 7805 data sheet (just Google "7805" to find one) will give you that info, under Absolute Maximum Ratings. For the Fairchild 7805 (the first one that comes up on Google), its 35 volts.

I used 9v input. is there current in it?

 

I used 9v input. is there current in it?

Ummm... not sure what you mean? 9V will certainly suffice as an input for the 7805, either from a 9V battery or from some other power source, such as a 9V DC wall-wart.

 

Not really sure what you mean either, but the current going into the regulator will be a few milliamps more than the current going into the load.