Are there many electronic engineers on this forum?
I regularly encounter problems when calculating the component values for a colpitts oscillator. There are a few online calculators available but some of these only accept values in Farad or Henry and in reality we are using values in the range of nH to mH and pF to uF. Also getting a capacitor value reported as 3.3051175983224774e-16 F is not really helpful. I have learned to first test the part values in LTspice because it often happened to me that the oscillator doesn’t start at all. Testing on a breadboard is the next step and then sometimes the frequency is a factor 1000 off.
So I asked an AI the question what is a good combination for an inductor and a capacitor to make an oscillator that always starts. It told me that the resonant frequency of the coil should be at least 10 times higher than the oscillator frequency and below 20 times.
A lot of work to get the proper values and asking for errors copying values from one calculator to the other.
So I started creating my own calculator on a single html page:
https://hennep.home.xs4all.nl/colpitts/
I could only find a single method to calculate the “Self-capacitance” of a single layer inductor and I don’t remember all the troubles I encountered but I have some questions, the list might grow a bit longer after this post:
- Is there a single best frequency for a coil instead of between 10x and 20x CRF, and how can that be calculated.
- Is there a method to calculate the “Self-capacitance” of multilayer inductors
- Are there any publicly available papers of Wheeler’s formulas