Simple switching regulator by LM358 , 78L05

This circuit uses a standard 78L05 low power 5v regulator in a novel way - as a voltage reference to a comparator. When the output voltage is LOWER than 5v, the output of the comparator switches high, turning on the transistor. The output voltage rapidly rises and once it is HIGHER than 5v, the output of the comparator switches low, turning off the transistor. The 0.33uF mono capacitor provides some smoothing and prevents oscillation in the multi-megahertz region. Under no load this circuit oscillates at about 32KHz. The diode and 470uF electro provide isolation and extra smoothing to produce an almost pure DC output.

Source : http://www.rowan.sensation.net.au/electronics/stepdown2.html

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