Techniques for improving performance of a transformer shared amongst a plurality of operating modes. In an aspect, first and second primary windings of a transformer are coupled to an AC ground voltage. Primary windings are mutually coupled to a secondary winding of the transformer. To render the second primary winding inactive, e.g., when operating in a first mode, a switch coupling the second primary winding to the common reference voltage is opened. Similarly, when it is desired to render the first primary winding inactive, e.g., when operating in a second mode, a switch coupling the first primary winding to the common reference voltage is opened. In this manner, the inactive primary winding advantageously does not load the secondary winding. Further aspects provide for, e.g., extending the techniques to more than two modes, and alternative techniques to mutually couple the signal from the primary to the secondary winding.