Design methodology and applications of SiGe BiCMOS cascode opamps with up to 37-GHz unity gain bandwidth

A new technique to design highly stable operational amplifiers with maximum unity gain bandwidth, UGB, is developed. It relies on biasing MOSFETs at the peak f/sub MAX/ current density. Several opamps, based on MOS-HBT SiGe BiCMOS cascodes, were designed and fabricated with UGB as high as 37 GHz. This record bandwidth is achieved with active p-MOSFET loads. A 1.3-GHz bandpass filter was implemented using two fully differential opamps with common-mode-feedback.