A traveling wave amplifier (TWA) comprising two or more amplification modules, the inputs of adjacent amplification modules being connected together by a first inductance component of a first characteristic impedance, a second inductance component of a second characteristic impedance and a third inductance component of substantially the first characteristic impedance, the first characteristic impedance being greater than the second characteristic impedance. The outputs of adjacent modules may be similarly connected together by first, second and third inductance components. The characteristic impedance of the second inductance components is preferably substantially equal to that of the circuits to which the TWA is connected, e.g. 50.OMEGA.. The first and third inductance components have a characteristic of 100.OMEGA.. Such a TWA allows balancing of phase velocities between inputs and outputs of the amplification modules, connection of these around via holes, and extends the frequency capability of the TWA.