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High Current Pass Transistor Configuration

Our favorite circuit. This one could handle up to 20 amps surge.

The upper left hand corner, of this schematic diagram, where it's marked "B+" is where you connect the rectified and filtered secondary voltage.

The upper right hand corner, of the schematic diagram, where it's marked "Vout" is where you connect the final output configuration of your finished power supply.

Down at the bottom of the schematic diagram, you will find a location labeled "Vreg in". This is the connection point for the "voltage out" of your voltage regulator circuit.

We chose to use 4 pass transistors and one driver transistor. This driver transistor takes the load off of the voltage regulator circuit. The 723 voltage regulator can only handle about 150 milli-amps of current. This configuration is good for around 20 amps or so, depending on the transformer that you have chosen.

You can add more, if you have a transformer that can handle more current than 20 amps. Or if you want the pass transistors to share more of a load. Sometimes more pass transistors are needed. The best way is to use the minimum that is needed to get the job done.

The 2n3771 transistors are good for a 20+ amp peak or surge. If you want the whole configuration to last a long time, I suggest that you keep the continuous current draw down to a minimum.

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