Cooling Case Fans to keep VCOs in tune?

yeah fair point I mention it on the site but not the BOM
its added to the to do list today after museum! cheerz


Tayda has a bunch of 1 nF options:

which includes:

  • Ceramic NP0/C0G (0±30 ppm/K), e.g. A-3524 (SMD), A-944 (SMD)
  • Polyester (PET) (200-600 ppm/K), e.g. A-557, A-1531, A-1987
  • Ceramic Y5P (±10% over −30/+85 °C) e.g. A-965
    • This is the “best performance” option on their “easy ordering page”.
  • Ceramic X7R (±15% over −55/+125 °C), e.g. A-3541 (SMD).

plus some unspecified types.

The last two are class 2 ceramics and are designed to be compact, at the expense of a high temperature coefficient; around 0.17%/K (or 1,700 ppm/K) on average across the full temperature range, but this is very much non-linear and can be several % at room temperature (see the chart in the comments here). These are great for decoupling/bypass, less so for timing.

I assume you ended up with one of the class 2 ceramics?

Ok, so before I had some regular ceramics with a 20% tolerance but I just got some C0G rated ones with a 1% tolerance from Mouser: #80-C410C102FAG5TA
Got them in there and it works beautifully now. Thank you all for your help with this!


It’s not the tolerance that’s the issue, really, it’s the temperature coefficient — which for these is very good, ±30ppm/°C from −55°C to +125°C. Even for the C440 ones that are 10% tolerance!

Good to hear it’s fixed!


Glad to hear it’s resolved!