[sdiy] There is no fun analogue chips anymore!

[Harry Bissell]

Its more a matter of dielectric.  If you are using COG (NP0) cermaics its a non-issue. For X5R or X7R
you need to decide if you can live with the reduction (or variation) of capacitance.

If you ~really~ care, use film capcitors. That's what they make them for...  :^)

H^) harry


----- Original Message -----
From: Dan Snazelle <subjectivity at hotmail.com>
To: Barry Klein <Barry.L.Klein at wdc.com>
Cc: sdiy diy <synth-diy at dropmix.xs4all.nl>
Sent: Fri, 29 Jun 2012 09:07:35 -0400 (EDT)
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
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy

-- 
Harry Bissell & Nora Abdullah 4eva