Component :
| Part | Total Qty. | Description | Substitutions | 
| R1, R4 | 2 | 2.2K  1/4W Resistor | |
| R2, R3 | 2 | 4.7K  1/4W Resistor | |
| R5 | 1 | 1K  1/4W Resistor | |
| R6 | 1 | 1.5K  1/4W Resistor | |
| R7 | 1 | 33K  1/4W Resistor | |
| R8 | 1 | 10K  1/4W Resistor | |
| C1,C2 | 2 | 0.1uF  Ceramic Disc Capacitor | |
| C3 | 1 | 470uF  25V Electrolytic Capcitor | |
| D1 | 1 | 1N914  Diode | |
| D2 | 1 | 1N4004  Diode | |
| D3 | 1 | 12V  400mW Zener Diode | |
| Q1, Q2, Q4 | 3 | BC547 NPN Transistor | |
| Q3 | 1 | BD679  NPN Transistor | |
| L1 | 1 | See  Notes | |
| MISC | 1 | Heatsink  For Q3, Binding Posts (For Input/Output), Wire, Board | 
Notes
1. L1 is a custom inductor  wound with about 80 turns of 0.5mm magnet wire  around a toroidal core  with a 40mm outside diameter.   
2. Different values of D3 can be used to get  different output voltages from  about 0.6V to around 30V. Note that at  higher voltages the circuit might not  perform as well and may not  produce as much current. You may also need to use a  larger C3 for  higher voltages and/or higher currents.   
3. You can use a larger value for C3 to provide  better filtering.   
4. The circuit will require about 2A from the 6V supply to  provide the full  800mA at 12V.          
Sourch
