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Output ripple of LM337

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: LM337

We have a question about LM337.

Vin=-5V

Vout=-2V

We use ceramic capacitor at input and output capacitor.

But output ripple increased.

Output ripple is reduced by adding 1.1Ω resistor at output capacitor.

(Please check the attached document.)

Why is output ripple reduced by adding 1.1Ω resistor at output capacitor?

Best regards,

Takahiro Nishizawa8688.LM337.pdf

  • 0
    TI__Guru 50090 points

    HI Nishizawa-san,

    The LM337 datasheet is not clear on output capacitor requirements. This device was created in an era where it was common to use polarized capacitors which tended to have a higher ESR (Equivalent Series Resistance) closer to 1-Ohm.  The ESR is required for stability. What you have done is a common recommendation to make it so low ESR ceramic capacitors can be used these older devices.

    Does this answer your question?