The Terahertz (THz) spectrum is the next frontier for efficient imaging applications and high-bandwidth wireless communication. A high-powered signal is imperative for the improvement of image resolution. The SiGe HBTs (heterojunction bipolar transistors) low output power level is one of the fundamental difficulties in the development of systems at high frequency and hence the importance of amplification at THz frequency range. This research is about designing, modeling, and simulating a 3-stage, 4-way power combined solid state PA (SSPA). The 3-stage design performance was optimized using a transmission line whose values were chosen optimally to ensure low loss. A single unit of the SSPA contains three stages and by using a splitter and combiner, 4 units of the SSPA were combined to give the desired output power. Simulations were performed using ADS Keysight and a gain of 30dB, saturation power out of 18.847dBm, and PAE (PAE) of 5.7% was achieved. This is a 28.8% increase in gain, an 11.36% increase in PAE, and a 3.3 % increase in saturation power compared to state-of-the-art results.