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how to plot the frequency v.s. differential bias curve

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jxzhang

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hello folks,


Anyone knows how to plot the frequency v.s. differential bias voltage curve of a VCO using spice script in HSPICE netlist?
differential voltage sweep from -0.4v ~ 0.4v

deeply appreciate ur advice
 

flushrat

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first run tran analysis and sweep the bias voltage
measure the delay of vco cell
then open .mt0 file with awaves
change x-axis to bias voltege and plot the measured delay
use f(x,y) function to plot frequency vs bias
 

jxzhang

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I've measured the delay by trig and targ and inversed to derive Fvco
and sweep the difference voltage in .tran
but I cannot find the measure type in awave
how to write the netlist for the differential control voltage sweep in .tran?
........

.param vcm=0.9
Vctlp VCP 0 dc='vcm + 0.5*vdif'
Vctlm VCM 0 dc='vcm - 0.5*vdif'
.......
.tran 100ps 10us start=0us UIC
+ sweep vdif lin 9 -0.4 0.4

.meas tran tvco trig v(CKP) val='supply*0.8' td=0.1us rise=100
+ targ v(CKP) val='supply*0.8' td=0.1us rise=111
.meas tran fvco param=('10/tvco')

what's wrong ?

Thanks!
 

Hughes

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jxzhang said:
I've measured the delay by trig and targ and inversed to derive Fvco
and sweep the difference voltage in .tran
but I cannot find the measure type in awave
how to write the netlist for the differential control voltage sweep in .tran?
........

.param vcm=0.9
Vctlp VCP 0 dc='vcm + 0.5*vdif'
Vctlm VCM 0 dc='vcm - 0.5*vdif'
.......
.tran 100ps 10us start=0us UIC
+ sweep vdif lin 9 -0.4 0.4

.meas tran tvco trig v(CKP) val='supply*0.8' td=0.1us rise=100
+ targ v(CKP) val='supply*0.8' td=0.1us rise=111
.meas tran fvco param=('10/tvco')

what's wrong ?

Thanks!
You have swept the differential voltage. Just plot the results in awaves.
 

flushrat

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what's your awaves version?
old version may not display measure results.
In new version, find fvco through results browser->types->measure->fvco
 

jxzhang

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version is ok, 2003.03
I can find the measure using single-ended control voltage type VCO
differential type as my netlist above cannot find it.
syntax error?
 

Hughes

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jxzhang said:
version is ok, 2003.03
I can find the measure using single-ended control voltage type VCO
differential type as my netlist above cannot find it.
syntax error?
Oh, I see.
Please change vdif to dif or _vdif or anything don't begin with letter v or i. Hspice treats names beginning with v as voltage source's instance name.
 

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