[sdiy] Using non-linear passives

[cheater00 cheater00]

The effect is much more dramatic than you say, and it seems to be easily
achievable. Here's a post by evilterrance at hotmail.com on the Electronics
101 mailing list:

> how about losing 80% of their capacitance by the time you are only
halfway to their voltage rating?  Look at the graph in the upper right:
>
>
https://product.tdk.com/info/en/documents/chara_sheet/C1608X5R1V225K080AC.pdf
>
> That +-10% tolerance?  Only counts to ONE volt.  To be fair, that is an
X5R...but look up your favorite X7R cap and check that DC bias curve.
Disappointing.

On Wed, 5 Apr 2017 17:25 Gordonjcp, <gordonjcp at gjcp.net> wrote:

> On Wed, Apr 05, 2017 at 03:04:19PM +0000, cheater00 cheater00 wrote:
> > Hi guys,
> > I've recently been reminded that ceramic caps (eg x5r) will only adhere
> to
> > their rating up to 1V, and will then start losing capacitance as you go
> > beyond. So effectively a DC bias could create a voltage controlled filter
> > just like that, with no semiconductors. I wonder, has anyone tried this?
>
> Not significantly.  I guess if you biased them up to a few kV you could
> get a couple of femtofarads of a swing out of it.
>
> Bear in mind that varicap diodes actually have a practical method of
> operation where the gap between semiconductor layers varies with bias
> voltage, and need about 30V to get a couple of pF out of them.
>
> --
> Gordonjcp MM0YEQ
>
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