This paper deals with the design and synthesis of active circuits able to simultaneously produce negative group delay and gain at microwave frequencies or for baseband signals. Analytical equations show that the proposed topology meets these objectives while also satisfying active device requirements. Then, a synthesis approach is extracted and applied to design a two stage microwave circuit, further validated by experimental results. This method is extended to the design of a four-stage baseband active circuit providing gain and negative group delay up to 600 MHz. A high relative time-advance is evidenced by time-domain simulations.