A coupled acoustic resonator adapted for single-ended input to differential output signal transformation, comprises a single stack. The single stack comprises: a first film bulk acoustic resonator (FBAR) comprising a single-ended input; a second FBAR disposed over the first FBAR comprising a first differential output and a second differential output; an acoustic decoupling layer disposed between the first FBAR and the second FBAR; and a resonant element comprising a resonant inductor and a parasitic capacitor connected in parallel. The resonant element is connected to the first differential output and is operative to substantially balance a signal from the first differential output with a signal from the second differential output. The first differential output is connected to an external circuit comprising a parasitic impedance, and the resonant inductor has an inductance selected to substantially maintain the balance.