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Hi,
I want to know how to measure input/output impedance of a device. Can I just do the s parameter analysis and then find out z parameters? Will that be enough?
Please add a voltage source for gate and sweep the voltage and check the current. Obtain impedance with V/I.
This is DC impedance.
If you want AC impedance, you need to sweep the frequency for every operating point.
Hi,
I have built a circuit with a small ac signal imposed on the dc bias voltage in the gate of the MOSFET and also a dc bias voltage at the drain. It does give me some result. But when I do the s parameter analysis on that device with same configuration and same bias conditions, the s parameter value does not match with the previous one.
Should it be an issue?
Operating point impedance is not worth much in a switching FET. The
gate impedance gets real "interesting" once the drain begins to slew.
Small signal analysis doesn't tell you much useful there. Even a linear
MOSFET amp is driven more by Cdg than lumped Cgg, without the
drain realistically loaded and free to move you'll get a bogus idea of
what the gate looks like to the driving source.
@dick_freebird I have not fully understood what you have said but if it is a matter to bias the mosfet in saturation region I did that, still there is discrepancy in the results.
@leo_o2 in s parameter analysis you can bias the MOSFET and then run the analysis
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