Gain Boosted D-Band CMOS Amplifier Using a Radial Stab for Source AC Grounding

To improve the CMOS amplifier’s gain in D-band, it is effective to use positive feedback. We focused on the positive feedback method by inserting a capacitor between the source of the FET and the ground. We proposed a new gain boost technique which uses a radial stub as the capacitor for positive feedback. By adding a short stub in parallel to the radial stub, DC path to the ground and stabilization in the lower frequency range are obtained. After the S-parameters comparison between FET with ideally grounded source and that with the radial stub, two types of 130 GHz amplifiers with two types of FETs have been fabricated in 65nm CMOS process. Both simulated and fabricated results show that the proposed amplifier has a gain more than 1.2 dB higher than a conventional amplifier.