@davidpgil Well, if you are looking to start from zero knowledge (Ohm's law, Kirchoff's laws) to the point where you can create PCBs (being able to deal with amplifiers, digital logic circuits, oscillators, feedback systems, frequency-domain analysis) — then I would suggest you to try learning it the hard way. Get the famous book named "Engineering Circuit Analysis" by Hayt, Kemmerly and Durbin (you can get it as PDF too); take a pen and a notebook, and study from it. Trust me, you will fall in love with the subject, and you won't find it hard. The only prerequisite is the knowledge of some high-school calculus.