Recently, there are revolutionary achievements in silicon-based conventional terahertz (THz) and millimeter-wave (mm-wave) integrated circuits, particularly with the advancement of CMOS technology. However, unlike Radio Frequency Integrated Circuits (RFICs), innovative designs and lack of various circuit techniques still remain unknown in THz gap. In this paper, a multi-band THz amplifier is presented in 40 nm CMOS technology with adaptive band selection technique. The smart amplifier is able to adjust the band of operation with respect to input signal power and frequency. In addition, the circuit performance will be adjusted to achieve maximum power gain. In order to achieve multi-band external neutralization, self-healing technique is vastly utilized by means of tunable transmission lines (TTLs). The proposed smart system contains tunable transmission lines, a 5-stage amplifier core, two Successive Approximation Register-based analog-to-digital converters (SAR ADCs), a digital control core and two on-chip power sensing blocks. The fabricated amplifier achieves P-1 of 1 dBm, P-sat of 6.1 dBm and power gain of 14.8 dB +/- <1.5 dB from 197 to 288 GHz frequency range. The proposed amplifier demonstrates the highest operation frequency among all published state-of-arts in all CMOS technologies.