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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> How to calculate and simulate impedance https://designers-guide.org/forum/YaBB.pl?num=1366228427 Message started by Larry_80 on Apr 17th, 2013, 12:53pm |
Title: How to calculate and simulate impedance Post by Larry_80 on Apr 17th, 2013, 12:53pm Hello Guys, Please How do i find Zin by hand calculation. Also how do i simulate the frequency dependent Zin in hspice? I would like to see if my Zin is a function (strong/weak) of the DC bias point (Vref) of my amplifier. |
Title: Re: How to calculate and simulate impedance Post by raja.cedt on Apr 17th, 2013, 1:22pm hello, I guess it should be nmos rather pmos. use small signal analysis, you will get around (1/sCdecap)+(ro)+(ro*1/scdecap*gm*(1+A)), of course it depends on vdd but as long as you have vddmin the sensitivity will be very less. Coming to simulation, you could use ac simulation, apply some ac voltage with proper dc voltage at vdd and find ac current. Thanks, Raj. |
Title: Re: How to calculate and simulate impedance Post by Larry_80 on Apr 17th, 2013, 1:31pm Thanks Raja, i was able to do the hand calculation. I will try to do the simulation now. Could i possibly do a network impedance simulation? |
Title: Re: How to calculate and simulate impedance Post by raja.cedt on Apr 17th, 2013, 1:33pm what do you mean by "network impedance simulation"? |
Title: Re: How to calculate and simulate impedance Post by Larry_80 on Apr 17th, 2013, 2:39pm raja.cedt wrote on Apr 17th, 2013, 1:33pm:
Sorry i meant like 2 port network analysis. Z11 will be the input impedance...considerng Vddm as the output. |
Title: Re: How to calculate and simulate impedance Post by raja.cedt on Apr 17th, 2013, 2:53pm yes, indeed that's very professional way of finding impedance at any node. Use S-parameter simulation or any two port sim and find the z11. Good night. |
Title: Re: How to calculate and simulate impedance Post by wave on Apr 18th, 2013, 3:30pm What is this circuit trying to accomplish?? It looks like an attempt at a DC bias circuit. Looks like there are problems. |
Title: Re: How to calculate and simulate impedance Post by tzg6sa on Apr 19th, 2013, 12:35am raja.cedt wrote on Apr 17th, 2013, 2:53pm:
Wouldn't it be enough to apply the AC source across the port? Of course with proper termination at the other ports if they exists. |
Title: Re: How to calculate and simulate impedance Post by raja.cedt on Apr 19th, 2013, 2:03am yes, sufficient. In fact i suggested the same in my first reply. Thanks, Raj. |
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