This paper describes a novel approach to system level analog design. A new abstraction level "the platform" is introduced to separate circuit design from design space exploration. An Analog Platform encapsulates analog components concurrently modeling their behavior and their achievable performances. Performance models are obtained through statistical sampling of circuit configurations. The design configurations space is specified with Analog Constraint Graphs so that the sampling space is significantly reduced. System level exploration can be achieved through optimization on behavioral models constrained by performance models. Finally, an example is provided showing the effectiveness of the approach on a WCDMA amplifier.