Full wave rectifier

Here the aim is to build a circuit that can give +12 volt supply from ac mains.Such a supply is a very common all those which used opamps.This circuit only produces +12 volt and other terminal is ground.This is can used for almost all the circuits described here.

Full wave rectifier


Part list
D1 & D2 1N4001 or Equivalent
C1 1000uf ,25Vsee notes
T1 12-0-12 see notes


The input transformer step downs AC main voltage from 230v or 110v (according to your location) to 12 v between the center tap and either of the two ends of the secondary winding .The transformer used has a capability of 250ma.

The 12VAC appearing across the secondary winding is RMS value of the wave forum and the peak value is 12 x 1.44 =16.8 volts.
The diodes D1 and D2 rectifies the waveform appearing at the secondary coil. The capacitors C1 provides the filtering action.

Here the two diodes D1 and D2 convert AC to pulsating DC which is then filtered by the capacitor C1.
Increasing the value of C1 increases the rectification; minimum value must be at least above 1000uf for ordinary circuits (higher values are required only if you are using this for a power amp or any other equipment’s that do something with audio).

If you need a different voltage change the transformer to your desired range.
Please keep the rating of the capacitor at least 10v above the required voltage.


The working can be explained by using simple physics. Let the top terminal be at positive cycle at a time t, Now the diode D1 is forward bias, this means that it will conduct, thus the out is available.but the diode D2 is in reverse bias.

During the other cycle i.e when top is in negative cycle the diode D1 is reverse biased it won’t conduct, at the same time the diode D2 is forward biased that will conduct and the out is again available. This continues making the output available at each cycle thus it gives a full time output.