A DC-2.5GHz voltage variable attenuator in 0.18-μm CMOS technology

A CMOS variable voltage attenuator(VVA) with wide bandwidth has been designed and fabricated in a 0.18-μm CMOS process. Four bridge-T stages are cascaded to achieve 12 dB of dynamic range attenuation over a frequency range from DC up to 2.5 GHz. Cascaded bridge-T stages can be programmed to achieve the full scale attenuation and ensure good input and output matching. The design operates with 1.5-dB step size and with a maximum input power of -13 dBm in the entire frequency DC-2.5 GHz range. Worst case S
₁₁
is -11.5 dB across the frequency band. The design achieves an input third order intercept point (IIP3) of+31 dBm at maximum-attenuation.