The disclosure relates to a signal combiner for a Doherty power amplifier architecture, the signal combiner including a termination circuit on an isolation port, the termination circuit being tuned to improve performance of the Doherty power amplifier. The architecture includes a carrier amplifier and a peaking amplifier. The peaking amplifier modulates the load seen by the carrier amplifier, allowing the carrier amplifier to remain in high-efficiency, saturated operation even at back-off. This load modulation can be achieved using impedance matching networks having an impedance matched to a specific frequency. The architectures include tuned or tailored signal combiners with termination circuits on isolation ports. The termination circuits are tuned or tailored for particular operating frequencies to enhance operation.