sgrjuneja
Newbie level 5
Hi,
I am designing LNA for GPS applications (1.57Ghz) using inductive source degeneration topology, circuit is attached. I mathematically calculated the values of Cgs, gm for the gain transistor taking Q = 4 and Rs - 50Ohms. Using this i calculated the value of Lg, Ls & W/L ratio of gain transistor. I am flowing Id = 6mA through gain transistor using a current mirror and my gm/Id ratio is between 10-15.
I implemented my design on Cadence Virtuoso tool at 180nm technology node (spectreRF version is MMSIM13.1).
DC analysis i am getting is correct as my theoretical and practical values of Cgs, Gm, Id etc match but my S parameter analysis is totally incorrect with S12 = S21 = -3B, S11 = S22 = -10dB, NF = 2.5dB at 1.6GHz. My results are attached
I request somebody to suggest what could possibly be wrong with my circuit.
I am designing LNA for GPS applications (1.57Ghz) using inductive source degeneration topology, circuit is attached. I mathematically calculated the values of Cgs, gm for the gain transistor taking Q = 4 and Rs - 50Ohms. Using this i calculated the value of Lg, Ls & W/L ratio of gain transistor. I am flowing Id = 6mA through gain transistor using a current mirror and my gm/Id ratio is between 10-15.
I implemented my design on Cadence Virtuoso tool at 180nm technology node (spectreRF version is MMSIM13.1).
DC analysis i am getting is correct as my theoretical and practical values of Cgs, Gm, Id etc match but my S parameter analysis is totally incorrect with S12 = S21 = -3B, S11 = S22 = -10dB, NF = 2.5dB at 1.6GHz. My results are attached
I request somebody to suggest what could possibly be wrong with my circuit.