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LC parallel circuit at resonant frequency

baristaskin

Dear All,

I am trying to simulate a simple LC parallel circuit when it is drived by a voltage source.

I'm expecting the current of the voltage source V1 to get smaller as its frequency gets closer to the resonant frequency.

When I simulate this circuit at the resonant frequency, with spectre default values, I get:

I tried to play around with the following parameters:

maxstep, reltol, vabstol, iabstol

without success.

My question is: how do I setup Spectre in order to get consistent and accurate results?

What I expect to see is a sine-shaped current signal with no DC value.

I'm including the netlist of the simulation shown above:

// Generated for: spectre
// Generated on: Mar 2 16:11:27 2015
// Design library name: paper3
// Design cell name: LC_osc
// Design view name: schematic
simulator lang=spectre
global 0
parameters _EXPR_8=1.986858915135295e-08 C=1p L=100n vdd=1 \
freqC=503.30696M cycles=10 L_IC=-sqrt(C/L)*vdd/2

// Library name: paper3
// Cell name: LC_osc
// View name: schematic
L1 (Vin 0) inductor l=L r=1a ic=0
V1 (Vin 0) vsource type=sine freq=freqC ampl=vdd/2 sinephase=90 sinedc=0
C1 (Vin 0) capacitor c=C ic=vdd/2
simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \
tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \
digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
checklimitdest=psf
tran tran stop=_EXPR_8 errpreset=conservative write="spectre.ic" \
writefinal="spectre.fc" annotate=status maxiters=5
finalTimeOP info what=oppoint where=rawfile
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
save Vin V1:p L1:1
saveOptions options save=allpub

 

Thank you in advance.

Parents

  • Dear Shawn,

    Thank you for your reply.

    The reason why I'm not using an AC analysis is because in my project I am using a non-linear circuit that I can't linearize.

    Here I was simply providing a minimum working example of the problem I run into when I simulate the circuit I'm working on.

    Very briefly, in place of the capacitor there is going to be a non-linear network (hundreds of transistors) that can be modeled, for the sake of simplicity, as a resistor in series with a capacitor.

    The Idea is to make this non linear system oscillate with the inductor, since RL can be fairly small.

    With such a system, and a required oscillation of 1V, I can't use AC analysis and I have to rely on transient.

    I need very high precision in the current solutions because I will use that data to compute the power consumption (ideally, when RL = 0 the power consumption is zero).

Reply

  • Dear Shawn,

    Thank you for your reply.

    The reason why I'm not using an AC analysis is because in my project I am using a non-linear circuit that I can't linearize.

    Here I was simply providing a minimum working example of the problem I run into when I simulate the circuit I'm working on.

    Very briefly, in place of the capacitor there is going to be a non-linear network (hundreds of transistors) that can be modeled, for the sake of simplicity, as a resistor in series with a capacitor.

    The Idea is to make this non linear system oscillate with the inductor, since RL can be fairly small.

    With such a system, and a required oscillation of 1V, I can't use AC analysis and I have to rely on transient.

    I need very high precision in the current solutions because I will use that data to compute the power consumption (ideally, when RL = 0 the power consumption is zero).

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