AUTO-TRANSFOMER, RADIO FREQUENCY DEVICE AND METHOD OF CONSTRUCTION OF AN AUTO-TRANSFOMER

A radio frequency, RF, auto-transformer circuit (300, 700, 901) and method (1000) of constructing a RF auto-transformer are described. The RF, auto-transformer circuit (300, 700, 901) includes: an inner coil formed (1102) with a first metal layer (MT1) to create a first shunt inductor (302), wherein at least a portion of the inner coil is overlayed (1106) with a second metal layer (MT2) that creates a first series inductor (303) that exhibits inductive coupling to the first shunt inductor (302). An outer coil is formed (1104) with the first metal layer (MT1) that creates a second series inductor (304), where the outer coil is located adjacent the inner coil and provides inductive coupling between the second series inductor (304) and each of the first shunt inductor (302) and first series inductor (303). At least a portion of the outer coil is overlayed (1008) with the second metal layer (MT2) that creates a second shunt inductor (301) that exhibits inductive coupling between the second shunt inductor (301) and each of the first shunt inductor (302) and first series inductor (303) and second series inductor (304). The outer coil is connected (1112) to the inner coil using vias and the respective first metal layer (MT1) is connected to the second layer (MT2) using vias.