Re: plus4 power supply

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Wed, 26 Sep 2012 17:26:32 +0200 Message-ID: <50631EA8.2010307@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 09/25/2012 10:11 PM, Hegedűs István wrote:
> Hi Gerrit,
>
> Reading back your posts I have one question. What is the purpose of the
> 100nF ceramic parallel to the 4700uF capacitor?

It's from the standard circuit for a 78xx-regulator. There you are 
supposed to put a ceramic capacitor between input and GND and output and 
GND. The idea, if I understand it right at least partially compensate 
for the rather 'slow' electrolytic capacitors in the case of fast load 
changes. Also, in the case of a real 78xx, they are supposed to keep it 
from oscillating.

You plan to put a switching regulator there, those produce fast load 
changed on the input side. A ceramic cap can't really hurt.

  Gerrit

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