I want to make transformer which can convert 220 volt ac to 20-0-20 volt Ac(Step Down) 6 Ampere for audio Amplifier. Now I have a question that For 6 Amp Calculation I should consider 3-0-3 Ampere for or 6 amp on both winding of Secondary or Whole Secondary winding with 6 Amp .

20-0-20 Whole winding 6 amp or I can use 3 amp winding for 0 to 20 and again 3 amp winding for 0 to 20 (20-0-20)

  • \$\begingroup\$ 20-0-20 (40 volt center tapped) at 6 amps will give you 240W. Is that the amount of power you want? Keep in mind if this is a half-wave rectifier, your transformer will need twice the power you mean to draw, since each half of the transformer is only used half the time. \$\endgroup\$ Commented May 2, 2016 at 3:14
  • \$\begingroup\$ yes its 240W but I will use Bridge Rectifier \$\endgroup\$
    – Alok Kumar
    Commented May 2, 2016 at 3:31
  • \$\begingroup\$ You could save a lot of guessing on our part by including the schematic of your power supply. There's a schematic button on the editor toolbar. \$\endgroup\$
    – Transistor
    Commented May 2, 2016 at 8:59

1 Answer 1


When a center tapped transformer is labelled with a particular current rating for its secondary, the number actually stands for the capability of the current carrying capacity of the copper wire in the secondary.

This means the each side of the transformer output is capable of delivering the labelled current.

In case of 20-0-20, 6A, if two outer ends of the transformer winding is connected to a bridge rectifier and the center tap is not used and no filter caps are installed, you will have 40 volt @ 6A (RMS).

If you use only one outer end and the center tap and connect it as above, you will have 20 volt @ 6 A (RMS).


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