20 Amp variable power supply with an output voltage from 1.5 to 15 volts using the LM317 regulator and 4 2N3055 power transistors to amplify the current capacity

This 12V to 9V DC converter is very useful for powering 9V DC devices in a car that uses 12V battery. The maximum current consumption allowed by this circuit is 0.8 amps.

This 1.5 V Joule Thief circuit can turn ON one LED. The circuit do not use a toroid coil, but it is possible to turn on a common red, green or yellow LED

This variable power supply uses the LM350 adjustable voltage regulator and can deliver 1.25 to 16 volts and a maximum current of 3 amps.

This Power source can be used to power circuits or electronic devices that would normally use a 9 volt battery, saving us the cost of the battery while being used at home.

4 Amp Variable Power Supply with 3 LM317 voltage regulators and a LM308 precision operational amplifier. Output voltage from 1.25 to 30 volts.

This variable power supply using an LM317 and a boost transistor can be useful when we need more current than the 1.5 amps that an LM317 can provide.

This 12V 1A power supply using zener diode and transistors allows us to obtain an output of approximately 11.4 volts with a very small percentage variation for a wide variety of loads.

15V power source ON delay using LM317. This circuit uses the LM317 voltage regulator. It also uses a transistor and an a electrolytic capacitor

This 12 VDC to -12 VDC converter circuit gives -12VDC (negative 12 volts) from a power source of + 12VDC (positive 12 volts), with very few components.