Amplifier circuit

An amplifier circuit 100 for use in a radio transmitter includes an RF power amplifier 101 and impedance matching means 117 and 119 for matching the input and output impedances of the power amplifier in a number of frequency bands. The amplifier 100 has an operational bandwidth greater than a decade, e.g. from 30MHz to 512MHz. The impedance matching means 117 and 119 each comprise a single LC section comprising switchable shunt capacitors (e.g. 181 - 189) and switchable series inductors (e.g. 161 - 169). The switches may be PIN diodes or FETs. A design algorithm for selecting the band start and end frequencies is disclosed; Q is maintained constant across all bands. The algorithm allows selection of component values so that a multi-octave frequency range may be covered by the single-section configuration.