Joule Thief Circuit: A DIY Experiment and Comparison
If you’ve never heard of a Joule Thief, it’s a simple voltage booster circuit that can power small loads like LEDs using a single battery, even ones that other devices consider “dead”.[Wikipedia article]
I built two versions of the Joule Thief circuit. One is the common version, using a single transistor, resistor, and coil, as shown in Wikipedia articles. The other version uses 2 transistors, 3 resistors, a capacitor, and an inductor, which I found online.[Here]
Both versions work well, but there are differences between them. The common version can operate at a lower voltage, around 0.6V, but consumes more current. The other version consumes much less current, 12mA, and 60mA at 1.3V, resulting in a slightly lower brightness, but with a small difference. In the common Joule Thief, I used a 2N4401 transistor, and in the other Joule Thief, I used a 2N3904 transistor.
During the experiment, I also tried to optimize their efficiency, observing their performance at different voltages. I found that both versions work well, but they have differences in voltage and current, and the right version should be chosen based on the actual situation.
