1 GHz opamp-based bandpass filter

A biquad bandpass filter, operating at 1 GHz with 9 dB gain, was designed and fabricated in 180nm SiGe BiCMOS technology. It relies on a 11-GHz unity-gain-bandwidth, highly stable opamp implemented using a MOS-HBT cascode stage with cascode p-MOSFET load and common-mode-feedback. The filter has tunable bandwidth and tunable center frequency and marks a radical approach to the design a bandpass filter operating in the gigahertz range.