OnSemi 317 and 337 recomended input capacitors are different?

Discussion in 'General Electronics Chat' started by dentaku, Mar 27, 2014.

  1. dentaku

    Thread Starter Member

    Jul 29, 2013
    I just breadboarded a power supply using an OnSemi LM317BT and OnSemi LM337T.
    The 317 datasheet has the regular 0.1uF cap on the input "*Cin is required if regulator is located an appreciable distance from power supply filter."
    I used a little round ceramic 104.

    BUT the 337 datasheet says "*Cin is required if regulator is located more than 4 inches from power supply filter.
    *A 1.0uF solid tantalum or 10uF aluminum electrolytic is recommended."
    I used a 10uF electrolytic

    You would assume that On Semiconductor manufactures the positive and negative regulators almost exactly the same way and that they would recommend the same input capacitor for both of them.

    What would be the reason for the difference in recommendations for the 317 and 337?
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
  3. #12


    Nov 30, 2010
    This is merely the facts of life. I am repeating myself when I say you will never memorize all of the capacitor values required for all the different regulators. That's what the datasheet is for.