#### kkantham

##### Newbie level 4

**ring oscillator**

hi guys i have a problem in transcient analysis of 3 stage simple ring oscillator in 45nm cmos technology. i got dc analysis but with 3rd inverter in saturation.

i could not get transcient curves and could not measure delay parameters. this is my netlist can any body help me in correcting this

netlist

------------------------------------------------------------------

.option ingold

.param vdd=1.1

.ic v(1)=vdd

***********************************************************************

* Subcircuits

***********************************************************************

.subckt inv a y vdd 0 n=90n p=180n

M1 y a 0 0 nmos l=45n w='n' ad='0.5u*n' as='0.5u*n' pd='1u+2*n' ps='1u+2*n'

M2 y a vdd vdd pmos l=45n w='p' ad='0.5u*p' as='0.5u*p' pd='1u+2*p' ps='1u+2*p'

.ends inv

***********************************************************************

* Simulation netlist

***********************************************************************

vdd vdd 0 dc 'vdd'

vin 1 0 dc

x1 1 2 vdd 0 inv

x2 2 3 vdd 0 inv

x3 3 1 vdd 0 inv

.dc vin 0 'vdd' 0.05

.plot dc v(1) v(2) v(3)

.print dc v(1) v(2) v(3)

.tran .1ns 10ns

.plot tran v(1) v(2) v(3)

.measure tran tpdr TRIG v(2) val='vdd/2' fall=1 TARG v(3) val='vdd/2' rise=1

.measure tran tpdf TRIG v(2) val='vdd/2' rise=1 TARG v(3) val='vdd/2' fall=1

.measure tpd param='(tpdr+tpdf)/2'

.OP

.probe

**library input files**

.include `45nm.inc`

.end

can any body please help me in correcting this netlist to prevent saturation and to oscilllate to get curves in .tran analysis