A drive unit for a synchronous ion shield mass separator having a reference oscillator (1), a digital direct synthesizer (2), a low-pass filter (3) and a comparator (4), wherein the synchronous ion shield mass separator has a comb-shaped separation electrode (6), the reference oscillator (1) provides the direct digital synthesizer (2) with a reference frequency, the output signal generated by the direct digital synthesizer is filtered by the low-pass filter (3) and the output signal of the low-pass filter (3) is processed by the comparator (4). A drive unit that can be applied flexibly and economically is implemented in that the output signal of the comparator (4) is converted by a programmable element (11) into a number of output signals corresponding to the number of teeth (7) of the comb-shaped separation electrode (6).