In 1982 he got drafted to the Swedish metal band Silver Mountain, and recorded a record with them. After weaselling out of military service in 1983, he left Sweden (and any academic ambitions) for California and joined guitarist Yngwie Malmsteen as a member of his band, Rising Force. Numerous records and world tours ensued, and he stayed with Yngwie until 1989. Jens also played with the band DIO between 1989 and 1990. Like Anders, he began an ongoing collaboration with Jonas Hellborg in 1989, which has resulted in several well-received progressive and avant-garde recordings, among many others Dissident (DEM 027), Silent Rain (DEM 028 -- an acoustic piano trio record with Ginger Baker on drums), and the hard core progressive fusion record E.
In 1993, Jens co-founded a progressive blues metal project, The Johansson Brothers, and recorded a self-titled record (ZERO XRCN 1127, ARCD 002). In 1996, with a different line-up, they recorded another one, Sonic Winter (Pony Canyon), this time under the name Johansson, with Yngwie guesting on guitar.
Since 1994 to present time, Jens has toured extensively with the progressive metal band Stratovarius and has also recorded three full-length albums with this group, Episode, Visions and Live in the Land of the Gods.
In 1995 he made the Heavy Machinery (HECD-011) record with guitarist Allan Holdsworth, also together with Anders. Jens has also released several instrumental solo records, such as Fjäderlösa Tvåfotingar (Amigo AMCD 872), Ten Seasons (HECD 008) and Fission (HECD 016).