[sdiy] LF398 and droop

[mark verbos]

I switched the caps to some polyester ones I had laying around and it  
looks like the problem is gone.  I also scratched the flux residue  
off the board. A guard ring isn't really possible now, but it seems ok.

Mark





On May 17, 2007, at 2:58 AM, Tim Parkhurst wrote:

> On 5/16/07, mark verbos <mverbos at earthlink.net> wrote:
>> How bad will a S&H build from an LF398 perform if a ceramic cap is
>> used? I built one using a .01 ceramic and I can actually watch the
>> voltage falling on the output. Is this the cap type? Am I missing
>> something?
>>
>> Thanks,
>>
>> Mark
>>
>
> Hey Mark,
>
> I've heard two things about S/H circuits:
> 1) Use Polystyrene or Teflon or Polypropelene caps.
> 2) Try to include a "guard ring" around the positive terminal of the
> cap on your pcb. See the 398 data sheet for examples.
> 3) Clean flux off of S/H circuits, as flux residue can create a high
> impedance leakage path for the charge on the cap.
>
>
> Tim (heard I can't count, either) Servo
> -- 
> "Imagination is more important than knowledge." - Albert Einstein