RF Transformer – the absolute basics

The RF transformer is a very useful device for the design of many types of RF circuits. It can be used as a device for changing voltage and current levels in a circuit and matching impedances.

This very brief post is simply a reminder of the absolute basic design equations for the RF transformer (and indeed, any transformer).

  1. n = N2/N1 , where n is the turns ratio of the two winding transformer. N2 and N1 are the number of turns of the secondary and the primary.
  2. V2 = nV1, V2 is the secondary output voltage, V1 is the primary voltage.
  3. I2 = I1/n. I2 is the current out of the secondary, I1 is the primary current.
  4. Z2 = n*n*Z1. Z2 is the impedance seen looking into the secondary and Z1 is the primary impedance. These are very basic quantities of an ideal transformer. For second and third order effects please see the equivalent circuit model of the  transformer. Please visit the SPG website for  more interesting information.

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