quick way to measure C-V curve

At least that's what it looks like on the Post-it note.

From a few larger parts I've checked I've gotten the impression they're deliberately making them on the lower edge of the tolerance band, even at 0V. If I read the part number correctly ;-) that's a 10% part, so it should be at least 42uF at 0V. John's number is lower.

--sp

In everything I ever read about designing power supplies, nobody ever said you have to make the cap 3x as large when filtering 15v. Were they holding back?

The capacitance spec is probably given for other frequencies than those resulting from John's test.

Pere

So, some electronics is built on LIES like that?

Well, if this isn't a real diamond ring, I just got cheated out of $15. ;)

Cheers

Phil Hobbs

Obamatronics, like Obamacare? 8-)

Another method would be to hang it in a Schmitt inverter oscillator in series with a really large film cap that is guaranteed not to have any C/V derating. Vary the voltage and log frequency or period. Then you only need one instrument since modern function gerenators can create DC levels (within reason) and also have a frequency/period counter built in.

How about a little jig? X-Y plot dV/dT against V?

-+- | .---[R]---. | | | | [i] V |\ | |\ | | | \ | | \ | +------------------+--|x1>----||-+-|- \ | | | | / | >---+-> dV/dT V | |/ .--|+ / V ||--' | | / | ||

Ceramic caps sure are.

The other Big Lie is mosfet power dissipation. IR started the practise of grossly inflating the power dissipation and current capability of their fets, and most everybody else went along to be competitive.

I just used what was in front of me on the bench.

It's surprising how often that the tool that you need is directly in reach. As long as you don't mind using, say, a dial caliper as a hammer.

And always have a Swiss army knife in pocket. In case something needs cutting, scraping, filing, prying, punching, stripping, poking, honing, loosening, or a bottle has to be opened.

Yes!! I added the necessary voltage output.

I've done that! Well, not in real life.

Samsung ceramic capacitors are notoriously bad. We always use Murata. They measure as advertised on the data sheet

Cheers

Klaus

Thanks Win, I added an oscilloscope!

(Sorry for the low-res screen shot.)

Cheers, James Arthur

Thanks, I added a printer output.

Hah! what do you guys think it's Friday? (And anyways James has the voltage going into the external trigger input and not channel 2. :^)

George H.

And a Toblerone chocolate bar, which every bench needs.