This paper presents a new Linear Power Amplifier (LPA) for a Series Hybrid Cascaded H-Bridge (SH-CHB) converter. The SH-CHB converter is used as a Power-Hardware-in-the-Loop (PHIL) system to emulate electrical grids and to analyze the behavior of converters. The concept of the SH-CHB converter is briefly introduced and the resulting requirements for the new LPA are discussed. The LPA is based on a novel symmetrical complementary Differential Input Stage (DIS). Unlike the standard DIS, this novel DIS has four independent inputs. This allows an H-Bridge interconnection of two LPAs, which increases the maximum slew rate of the output. Due to the high output current of the PHIL system, a highly efficient cooling concept for the Output Stage (OS) of the LPA is implemented. Experimental results of the designed LPA are given. Furthermore, feasible applications for the novel DIS are described and the benefits compared to conventional systems are elaborated.