The camshaft phaser is affixed to one end of a concentric camshaft. The phaser is a vane-type camshaft phaser where the stator and the sprocket are fixed to the outer camshaft and the trigger wheel and rotor are fixed to the inner camshaft. The torsion spring is mounted on an outer wall of the stator, between the stator and the trigger wheel. The phaser is a compact unit with a high degree of reliability.