A combiner circuit for a class-E outphasing power amplifier comprising first and second branch amplifiers, the combiner circuit comprising: a first input node, for receiving the output signal of the first branch amplifier; a second input node, for receiving the output signal of the second branch amplifier; and an output node, for supplying a combined output signal to a load; a first inductor (L E) connected at the first input node, the first inductor having an input terminal connected to the first input node and an output terminal; a second inductor (L E) connected at the second input node, the second inductor having an input terminal connected to the second input node and an output terminal; the combiner circuit characterised by: a compensation inductor (L CHIR) coupled in series with the first inductor and connected to the output node; a compensation capacitor (C CHIR) coupled in series with the second inductor and connected to the output node; a first capacitor (C E), with one terminal connected to the output terminal of the first inductor and the other terminal connected to ground; and a second capacitor (C E), with one terminal connected to the output terminal of the second inductor and the other terminal connected to ground, wherein the second capacitor and the compensation capacitor are implemented as Metal-Insulator-Metal capacitors together on a single die and wherein each of the capacitors and/or inductors is implemented as a lumped element component. a first input node, for receiving the output signal of the first branch amplifier; a second input node, for receiving the output signal of the second branch amplifier; and an output node, for supplying a combined output signal to a load; a first inductor (L E) connected at the first input node, the first inductor having an input terminal connected to the first input node and an output terminal; a second inductor (L E) connected at the second input node, the second inductor having an input terminal connected to the second input node and an output terminal; the combiner circuit characterised by: a compensation inductor (L CHIR) coupled in series with the first inductor and connected to the output node; a compensation capacitor (C CHIR) coupled in series with the second inductor and connected to the output node; a first capacitor (C E), with one terminal connected to the output terminal of the first inductor and the other terminal connected to ground; and a second capacitor (C E), with one terminal connected to the output terminal of the second inductor and the other terminal connected to ground, wherein the second capacitor and the compensation capacitor are implemented as Metal-Insulator-Metal capacitors together on a single die and wherein each of the capacitors and/or inductors is implemented as a lumped element component. a compensation inductor (L CHIR) coupled in series with the first inductor and connected to the output node; a compensation capacitor (C CHIR) coupled in series with the second inductor and connected to the output node; a first capacitor (C E), with one terminal connected to the output terminal of the first inductor and the other terminal connected to ground; and a second capacitor (C E), with one terminal connected to the output terminal of the second inductor and the other terminal connected to ground, wherein the second capacitor and the compensation capacitor are implemented as Metal-Insulator-Metal capacitors together on a single die and wherein each of the capacitors and/or inductors is implemented as a lumped element component.