# no convergence in dc sweep curves [closed]

I have a question. I'm trying to simulate a ring oscillator with variation on Vth ,..., in hspice, but I get no convergence in dc sweep curves error. I tried some of solutions to convergence, but have not got any success, can you help me. The netlist & the errors are as followings:

V1 vdd 0 0.9V
V2 vss 0 0V

.PARAM bias=1m
MN11 vss 15 11 vss N1 L=120n W=280n x=-7000u y=2000u
MP11 vdd 15 11 vdd P1 L=120n W=980n x=-7000u y=6000u
MN12 vss 11 12 vss N1 L=120n W=280n x=-5500u y=2000u
MP12 vdd 11 12 vdd P1 L=120n W=980n x=-5500u y=6000u
MN13 vss 12 13 vss N1 L=120n W=280n x=-4000u y=2000u
MP13 vdd 12 13 vdd P1 L=120n W=980n x=-4000u y=6000u
MN14 vss 13 14 vss N1 L=120n W=280n x=-2500u y=2000u
MP14 vdd 13 14 vdd P1 L=120n W=980n x=-2500u y=6000u
MN15 vss 14 15 vss N1 L=120n W=280n x=-1000u y=2000u
MP15 vdd 14 15 vdd P1 L=120n W=980n x=-1000u y=6000u

.MODEL  N1  NMOS  LEVEL = 54
.MODEL  P1  PMOS  LEVEL = 54

.Variation
.Global_Variation
Parameter var=N() Y='180 + 8.02 * var' Z='17.5 + 0.37 * var'
Nmos N1
+ VTH0=Perturb('Y')
Pmos P1
+ VTH0=Perturb('Y')
.End_Global_Variation
.Local_Variation
Parameter var=N() T='11.46 * var' U='0.54 * var'
Nmos N1
+ VTH0=Perturb('T')
Pmos P1
+ VTH0=Perturb('T')
.End_Local_Variation

.End_Variation

.op

.dc bias 1m 1m 1m monte=10
.print I(MN11) I(MN12)
.measure dc I11 find I(MN11) at=1m
.measure dc I12 find I(MN12) at=1m

.END


dcop: begin pseudo transient
dcop: ...failed with iteration exhausted
dcop: end pseudo transient
dcop: gshunt =      0.1000000E-03
dcop: gshunt =      0.5050000E-03
dcop: gshunt =      0.7277500E-03
dcop: gshunt =      0.8502625E-03
dcop: gshunt =      0.9176444E-03
dcop: gshunt =      0.9547044E-03
dcop: gshunt =      0.9750874E-03
dcop: gshunt =      0.9862981E-03
dcop: gshunt =      0.9924639E-03
dcop: gshunt =      0.9958552E-03
dcop: gshunt =      0.9977203E-03
dcop: gshunt =      0.9987462E-03
dcop: gshunt =      0.9993104E-03
dcop: gshunt =      0.9996207E-03
dcop: gshunt =      0.9997914E-03
dcop: gshunt =      0.9998853E-03
dcop: gshunt =      0.9999369E-03
dcop: gshunt =      0.9999653E-03
dcop: gshunt =      0.9999809E-03
dcop: gshunt =      0.9999895E-03
dcop: gshunt =      0.9999942E-03
dcop: gshunt =      0.9999968E-03
dcop: gshunt =      0.9999983E-03
dcop: gshunt =      0.9999990E-03
dcop: gshunt =      0.9999995E-03
dcop: gshunt =      0.9999997E-03
dcop: gshunt =      0.9999998E-03
dcop: gshunt =      0.9999999E-03
**error** no convergence in dc sweep curves at  1.00000E-03


I ask you to help me.

## closed as unclear what you're asking by Olin Lathrop, dim, Bence Kaulics, Autistic, Daniel GrilloJul 8 '16 at 13:41

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• Show a schematic so we don't have to decode you spice code. Not everyone has Hspice – Voltage Spike Feb 1 '16 at 21:13
• A ring oscillator has no stable DC operating point. Perhaps @laptop2d's suggestions will allow you to move past that obstacle... – Brian Drummond Feb 1 '16 at 21:37
• I want to measure leakage current of a ring oscillator with variation on Vth, in 45 nm node technology. variation is a gaussian distribution with a mean and sigma, ( T & Y in the code). I do a monte carlo simulation as is mentioned in the code. So the result must be a distribution of leakage currents. – lili94 Feb 2 '16 at 12:43