weigiho
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Posts: 8
Austin
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I simulate a common-source amplifier with a capacitor load CL. Its drain is connected to VDD through an ideal current source. The input freq is high so that I cannot neglect the effect of parasitic capacitance. I am interested in finding the drain voltage. By using DC analysis, I can find all the parameters, such as gm, gds, Cdd, Cdg, Cdb and Cds. I use vd=vin*gm/(gds+jωCL+jωCdd)
to find vd. My calculated value is 2.3951e-5. But the transient simulation+FFT gives me 1.32131e-5. Why there is a big difference? The possible reason I guess is
(1)Should I use Cdd here? If yes, do I have to consider Miller effect? (2)There are other parameters, such as Cddbi and Cgdovl. I do not know what they mean so I did not include them at all. Is this the reason for the big difference?
Thanks a lot in advance.
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