This work reports a concurrent dual-band amplifier with an extensive spacing between the two bands by adopting a proposed dual-frequency maximum achievable gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G_{\max }$</tex-math></inline-formula> ) core with dual-band matching. The proposed dual-frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G_{\max }$</tex-math></inline-formula> -core can expand the difference between the two target frequencies by focusing on satisfying dominant gain-boosting condition and adopting a linear, lossy, and reciprocal-based design approach. Implemented in a 65-nm complementary metal-oxide-semiconductor (CMOS) process, a five-stage dual-band amplifier shows a peak power gain of 23.6 and 13.7 dB, 3 dB bandwidth of 5 and 17 GHz, saturated output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{\text{sat}}$</tex-math></inline-formula> ) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 1.2 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 2.2 dBm, and peak power-added efficiency of 2.1 and 1.5 % at 201 and 283 GHz, respectively, while consuming a dc power of 34.5 mW. The proposed amplifier is the first demonstration of the concurrent dual-band amplifier operating at G- (140–220 GHz) and H- (220–325 GHz) bands.