This paper presents a 150GHz fully differential amplifier with gain boosting and optimized Marchand balun matching networks in a 65nm CMOS technology. The optimized Marchand balun overcomes the self- resonance problem that the conventional balun suffers, and reduces the size as well. The over- neutralization technique is proposed and utilized in order to boost the gain of a differential pair without extra penalty on power consumption. A four- stage amplifier achieves a maximum gain of 19.2dB at 150GHz with a 3dB bandwidth of 14GHz, while consuming 48mW of power from a 1.2V supply.