We demonstrate the generation and detection of subpicosecand pulses by photoconductive sampling in a three-line coplanar transmission line structure. Due to a mutual inductive coupling between adjacent striplines a differential sampling is obtained. Voltage pulses as short as 390 fs have been measured in a lung-lifetime photoconductive with. We emphasize that differential coupling can be used for the detection as well as the generation of subpicosecond pulses in long-lifetime photoconductors. (C) 1996 American Institute of Physics.