A current waveform generator

A current generator (111) comprising a plurality of current cells (209_1 to 209_n, 223_1 to 223_n) connected in parallel, each current cell (209_1 to 209_n, 223_1 to 223_n) being connected to a switch (213_1 to 213_n, 227_1 to 227_n); a first summer configured to sum the output of each current cell of a first subset (207) of the plurality of current cells (209_1 to 209_n) and a second summer configured to sum the output of each current cell (223_1 to 223_n) of a second subset (221) of the plurality of current cells; a combiner (219) configured to combine the outputs of the first and second summers; and wherein each switch (213_1 to 213_n, 227_1 to 227_n) is switchable according to a sequence to generate a summed output I 1 I 2 of the current cells at a plurality of quantisation levels to generate positive and/or negative alternations of a pseudo-sinusoidal, alternating current.