An apparatus comprising: a power amplifier configured to amplify an input radio frequency, RF, signal and provide an amplified RF signal; and an impedance matching circuit coupled to the power amplifier and configured to match an output impedance of the power amplifier, the impedance matching circuit comprising at least one tunable notch filter dynamically adjusted during operation in response to a selection of stored settings from a look up table for a new operating band of the RF input signal, said dynamically adjusting attenuating at least one undesired signal in the amplified RF signal, the at least one tunable notch filter comprising an adjustable capacitor (662, 664, 666, 668, 714, 716, 724, 730, 744, 752, 810), said look-up table configured to receive an indication of a current operating frequency, and provide one of the stored settings corresponding to the current operating frequency for each of the at least one tunable notch filter; the adjustable capacitor (662, 664, 666, 668, 714, 716, 724, 730, 744, 752, 810) comprising: a first switchable capacitor (830a, 832a) having a first capacitor size; a first plurality of transistors coupled in a stack to the first switchable capacitor and having a first transistor size; a second switchable capacitor (830b, 832b) having a second capacitor size; and a second plurality of transistors coupled in a stack to the second switchable capacitor and having a second transistor size. a power amplifier configured to amplify an input radio frequency, RF, signal and provide an amplified RF signal; and an impedance matching circuit coupled to the power amplifier and configured to match an output impedance of the power amplifier, the impedance matching circuit comprising at least one tunable notch filter dynamically adjusted during operation in response to a selection of stored settings from a look up table for a new operating band of the RF input signal, said dynamically adjusting attenuating at least one undesired signal in the amplified RF signal, the at least one tunable notch filter comprising an adjustable capacitor (662, 664, 666, 668, 714, 716, 724, 730, 744, 752, 810), said look-up table configured to receive an indication of a current operating frequency, and provide one of the stored settings corresponding to the current operating frequency for each of the at least one tunable notch filter; receive an indication of a current operating frequency, and provide one of the stored settings corresponding to the current operating frequency for each of the at least one tunable notch filter; the adjustable capacitor (662, 664, 666, 668, 714, 716, 724, 730, 744, 752, 810) comprising: a first switchable capacitor (830a, 832a) having a first capacitor size; a first plurality of transistors coupled in a stack to the first switchable capacitor and having a first transistor size; a second switchable capacitor (830b, 832b) having a second capacitor size; and a second plurality of transistors coupled in a stack to the second switchable capacitor and having a second transistor size. a first switchable capacitor (830a, 832a) having a first capacitor size; a first plurality of transistors coupled in a stack to the first switchable capacitor and having a first transistor size; a second switchable capacitor (830b, 832b) having a second capacitor size; and a second plurality of transistors coupled in a stack to the second switchable capacitor and having a second transistor size.