This Power Supply was designed as an easy Project to get used to soldering - and at the end - have something useful. The fact that factories stop producing linear Power Supplies makes it even more interesting.

The torid transformer has its secondary center tap grounded. By that we can get away with only 4 diodes and still have approx. ± 20 Vdc.

With two large capacitors of 2200 µF, the voltage is smoothed. The current limiting is done with an opamp (LM10), a pass transistor (TIP-152) and a shunt resistor (0.33 Ω). As the LM10 has an internal reference voltage of 0.2 V, the absolute maximum current is 0.2 V / 0.33 Ω = 606 mA. (Specifications are always made lower, so the customer is happy, discovering that the devices delivers more for the same price :-)

Following the current limiting section are two standard voltage regulators 7815 and 7915 in a TO-220 case which has an internal current limit of max. 1.5 A - that would have been too much for this small transformer.

The Measurement Setup as well as other devices can be found here : Ripple and Noise Measurements.

UNIT	RANGES • REMARKS
Specifications	+/- 15 V, 600 mA
Type	Dual Linear Power Supply
Worst Spur	-65.42 dBV @ 150 Hz (Ripple), negative branch
Load was	15 V, 250 mA
Remarks	each branch tested single

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