An MMIC twin-tee active bandpass filter

The design and performance of an MMIC (monolithic microwave integrated circuit) active bandpass filter based on a twin-tee notch circuit are described. Design goals included a center frequency of 2 GHz and a Q that could be varied to well over 100. The device was fabricated in GaAs using 150- mu m transistors. Die size is approximately 1 mm/sup 2/, and power dissipation is approximately 180 mW. Although Q values meet expectations, the measured center frequency (1.35 GHz) is low. Speculation as to the cause of the difference focuses on the capacitance values of the twin-tee circuit.<>