Patent ID: 7388455

Claim:
A film acoustically-coupled transformer (FACT), comprising: a first decoupled stacked bulk acoustic resonator (DSBAR) and a second DSBAR, each DSBAR comprising: a lower film bulk acoustic resonator (FBAR) and an upper FBAR, the upper FBAR stacked atop the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, and an acoustic decoupler between the FBARs; a first electrical circuit interconnecting the lower FBARs; and a second electrical circuit interconnecting the upper FBARs; in which: in at least one of the DSBARs, the acoustic decoupler, one of the electrodes of the lower FBAR adjacent the acoustic decoupler and one of the electrodes of the upper FBAR adjacent the acoustic decoupler constitute a parasitic capacitor; and the FACT additionally comprises an inductor electrically connected in parallel with the parasitic capacitor.