No input voltage to the LM317 regulator?

Status
Not open for further replies.

khouly

Advanced Member level 5
Joined
Oct 20, 2003
Messages
2,350
Helped
461
Reputation
916
Reaction score
102
Trophy points
1,343
Location
EGYPT
Activity points
13,242
about LM317

i saw a circuit using the regulator LM317
but the strange thing about it
i saw that when there is NO input voltage to the regulator , and i inserted a voltage on the output node , i found that the input of the regulator have a voltage and not isolated is this normal issue or not

and is this condition will defect the LM317

khouly
 

Re: about LM317

You will not damage the LM317 by connecting a voltage to its output, and this voltage will penetrate to the input pin (normal behaviour) ..
In some circumstances it is wise to connect a protective diode between output (anode) and input (cathode), and this diode will protect LM317 from rapid discharge from output to input pin in case input pin is shorten to 0V ( for example, big cap connected between input pin and 0V) ..

Regards,
IanP
 

    khouly

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…