Harpo
Well-known member
Hallo out there,
maybe someone can proove this concerning the cap from adjust to ground to improve ripple-rejection at about 15 dB.
All LM317-datasheets I read (Vishay,National,Fairchild,SGS-Thomson)state this to be 10 uF as a type of constant, but all have a 240 Ohm resistor for R1 and receive power from a 60Hz line.
This R-series / C to ground seems to be a low-pass for 120Hz behind rectifier, set for 3dB at 60Hz (+12dB for 120Hz giving the desired 15db rejection).
For C = 1 / (2*pi * R * F) will get 11,05uF, this will be close to the stated 10uF (constant?).
In case you lower R1 to maybe 120 Ohm and have european 50Hz supply, this value would increase to 26,5uF for this 15dB loss at 100Hz.
Couldn't find this in the meta and have no instruments to proove myself.
I hope, I did'nt mix things up and better have asked for brain-adjustment.
All the best
Harpo
maybe someone can proove this concerning the cap from adjust to ground to improve ripple-rejection at about 15 dB.
All LM317-datasheets I read (Vishay,National,Fairchild,SGS-Thomson)state this to be 10 uF as a type of constant, but all have a 240 Ohm resistor for R1 and receive power from a 60Hz line.
This R-series / C to ground seems to be a low-pass for 120Hz behind rectifier, set for 3dB at 60Hz (+12dB for 120Hz giving the desired 15db rejection).
For C = 1 / (2*pi * R * F) will get 11,05uF, this will be close to the stated 10uF (constant?).
In case you lower R1 to maybe 120 Ohm and have european 50Hz supply, this value would increase to 26,5uF for this 15dB loss at 100Hz.
Couldn't find this in the meta and have no instruments to proove myself.
I hope, I did'nt mix things up and better have asked for brain-adjustment.
All the best
Harpo