[sdiy] There is no fun analogue chips anymore!

[Paul Schreiber]

Required reading:

http://www.electrical-integrity.com/Paper_download_files/EPEP03_cap_models_poster.pdf

http://www.electrical-integrity.com/Paper_download_files/DC11_13-TH2Paper_Novak.pdf

or as I like to call it "What they leave off the data sheets".

Paul S.
/former TDK capacitor FAE
//Shhhh...it's a secret.....sigh......




-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Dan Snazelle
Sent: Friday, June 29, 2012 8:08 AM
To: Barry Klein
Cc: sdiy diy
Subject: Re: [sdiy] There is no fun analogue chips anymore!

On Jun 28, 2012, at 4:19 PM, Barry Klein <Barry.L.Klein at wdc.com> wrote:

> Many designers don't realize that effective capacitance drops often 50% with DC across multilayer type ceramics - and this varies between manufacturers and voltage ratings.
> I hadn't come across any that got worse over time though.  Any background on this - a particular vendor?
> 
> Barry
> 
> 


Woa! This sounds like a potential nightmare.

So does this mean that I should not use ML caps in parts of my circuits where Dc exists? Can you explain this more? 

Are plain old (cheap brown disc) ceramics at risk also?


Thanks



> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Gordon JC 
> Pearce
> Sent: Thursday, June 28, 2012 12:26 PM
> To: sdiy diy
> Subject: Re: [sdiy] There is no fun analogue chips anymore!
> 
> On 28/06/12 20:16, Pete Hartman wrote:
>> So I have displayed my ignorance publicly again :-)
>> 
>> Thanks for the pointers.  Glad to see it's not as complicated as I 
>> had thought from some long past exposure to things like "flowing 
>> solder with a toaster oven".
>> 
>> Pete
> 
> http://www.gjcp.net/~gordonjcp/capacitor.jpg
> 
> That was taken with a cheapy USB microscope.  It's an 0.1μF ceramic capacitor in a Kenwood HT, part of the mic preamp, and like all little ceramic caps prone to going leaky if there's a DC voltage across them - like, uh, the preamp bias voltage.  The replacement in the picture was hand-soldered, cleaned up with some flux cleaner, and you'd hardly tell it had been touched.  I used a fairly pointy soldering iron tip and some tweezers that I'd reshaped a little to be better at picking up tiny grain-of-sugar components.  I didn't use the USB microscope because it is too "laggy" to update.
> 
> Now, I don't need glasses, but I'm 38 and I can tell my eyesight isn't 
> as sharp as it was ten years ago ;-)
> 
> It's not that hard...
> 
> --
> Gordonjcp MM0YEQ
> 
> 
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