Hi, radiohead:
This is ATF-54143 reference design. Have you ever used this circuit to design LNA with ATF-54143?
I have doubt about this circuit:
Please check these two Application notes:
High Intercept Low Noise Amplifier for the 1850 – Please check these two 1910 MHz PCS Band using the Agilent ATF-54143 (5988-2336EN)
High Intercept Low Noise Amplifier for 1.9 GHz PCS and 2.1 GHz WCDMA Applications using the ATF-55143 (5988-3399EN)
In these two Application notes, Agilent gives the same layout and the nearly the same input matching network, the same inductor L1 and the same cap C2, the only different is the C1, which is 8.2Pf for 54143 and 5.6pf for 55143.
But ATF-54143 at bias of Vds=3V, Id=60mA have very different S11 and Sopt from ATF-55143 at the bias of Vds=2.7V, Id=10mA.
I have tried to simulate Agilent’s ATF-54143 reference circuit with ADS, the result is really bad. And you can check the bias resistor R3, the R3 should be 33Ohm not 10 Ohm when Vdd=5V and bias of 3V@60mA.
Has anyone tried agilent’s reference design? Does it work well?
And in a small signal S-parameter simulation, R4 and C3 should also be included in the schematic? And how about the microstrip lines between L1, R4, C3? should them be included in the schematic too?
R4: stability at low frequencies
C3: low frequency decoupling cap