1. A configurable memristive device ( 300 ) for regulating an electrical signal comprises: a memristive matrix ( 350 ), said memristive matrix ( 350 ) containing a first dopant species; an emitter electrode ( 320 ), a collector electrode ( 310 ) and a base electrode ( 340 ), said electrodes being in electrical contact with said memristive matrix; and a mobile dopant species, said mobile dopant species being contained within a central region ( 360 ) contiguous with said base electrode ( 310 ), said mobile dopant species moving within said memristive matrix ( 350 ) in response to a programming electrical field.