# ps2_2014_ADS - ECE 145a/218A problem set(device models 2...

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1 ECE 145a /218A problem set (device models, 2 port parameters, impedance matching). Note: please download the ADS directory ADS_for_218a, unarchive this in ADS, and use this for the simulation portion of the assignment. Problem 1: Shown is a highly simplified small-signal model of a MOSFET. Ri=0 Ohms, gm=200 mS, Rds=100 Ohms, Cgs=100 fF, Cgd=0 fF The source is grounded. a) Compute by hand the four Y-parameters as a function of frequency. b) create a 2-port circuit of this device in ADS. Simulate using the provided gain_testbench, and make plots of the real and imaginary parts of the 4 Y-parameters. Use linear scales for both axes. Problem 2 (218A only): Now set Ri=10 Ohms, gm=200 mS, Rds=100 Ohms, Cgs=100 fF, Cgd=5 fF. a) Again compute the 4 Y-parameters (real and imaginary parts) by hand. Use numerical approximations so that all four of these are written as polynomials in nj)(, and truncate the polynomials to 2nd order in )(j. Comment about how the effects of the various circuit elements show up in the Y parameters.