The joule thief runs in a relaxation oscillator mode, as a “blocking oscillator”. The inductance of the LC-circuit in the joule thief is part of the transformer and the capacitance is hidden in the parasitic effects of the components, mainly the transformer and the pn-junctions of the transistor contribute to the capacitance. “Defining an electronic oscillator by its type of feedback, an oscillator with magnetic coupling (transformer) is an Armstrong/Meißner oscillator. People with a more mathematical background often use different definitions than people with a more circuit experience based background.” “Wording is always difficult in electronics. I heard back from a query to the authors of the paper that is cited on Wikipedia. I’m going to write this up in the discussion section of this wiki. One might claim that it has stray capacitance, but at the very low switching rate – less than 100 kHz – at which the Joule Thief switches, the few pF of stray capacitance is insignificant it plays no part in the circuit’s operation. The Joule thief does not have any capacitance, therefore it is not an Armstrong oscillator. In the Wikipedia article for Armstrong Oscillator, it says “inductance and capacitance” (my emphasis). I don’t know what Wikipedia’s policy is on this, but to me it’s unethical and a worthless reference.Īlso, I don’t believe that this is an Armstrong oscillator. What we have is a case of one article supporting the other, with no factual support from any ‘foundation’ article, hence no actual factual support. This article then points back to Wikipedia as a reference. This refers to an article which describes this as an Armstrong or Meissner oscillator. I was looking at the references in the Joule Thief Wiki at Wikipedia, especially the first reference, after “Armstrong” in the first line of the text.
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