ps2_ADS.pdf - 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=50 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=50 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 n j ) ( , 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.

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