This paper presents a design of a CMOS D-band high gain and wide bandwidth amplifier adopting the dual-peak Gmax technique. The proposed amplifier applies the dual-frequency Gmax technique based on 3-embedding, which provides high gain over a wide bandwidth. By utilizing the degree of freedom of 3-embedding, we designed a core with optimal input and output impedance. After that, a D-band 3-stage power amplifier is constructed using the designed Gmax-core. When VDD=1V, the measured gain peaks 16.8 dB at 161 GHz with the 3-dB bandwidth of 18.6 GHz and the operating frequency from 150.2 GHz to 168.8 GHz. The maximum output power is 5.65 dBm at 159 GHz and shows performance ranging from 1.39 to 5.65 dBm across the entire operating frequency range. The DC power consumption is 98 mW. The total chip area of the power amplifier is 0.224 mm².