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LM4120: Negative Output Circuit

Prodigy 20 points

Cheryl Kung

Part Number: LM4120

Has anyone else tried the Negative Output Circuit for this regulator, as shown on Figure 19 of the datasheet? We've been trying to get this to work consistently, but it's only worked a few times. It works fine for the positive output circuit, though.

Prodigy 20 points

Cheryl Kung

• Apr 12, 2017 11:18 PM
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2 Replies

• Intellectual 940 points

  

  Diego Lewis

  

  • Apr 13, 2017 11:00 PM

  Hi Cheryl,
  
  What values are you using for the input capacitor and resistor from Figure 19? Additionally, are you using any load capacitors? That figure doesn't show one, but I believe the part still needs a load capacitor for stability (between Vout and GND, like in Figure 29).
  
  What about the values in the positive output case (Figure 29)?
  
  Regards, Diego Lewis

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• Prodigy 20 points

  

  Cheryl Kung

  

  • Apr 14, 2017 7:59 PM

  In reply to Diego Lewis:

  Hi Diego,

  I'm using a 1K resistor and 0.1uF capacitor, like Figure 19 suggests. There's no load capacitor, but I'll try it and see if that works.

  The positive output case works fine.

  Thanks,

  Cheryl

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