Saturday, 4 October 2014

CNTFET Inverter "Design & Simulation using HSPICE"

Carbon Nanotube Field Effect Transistor(CNTFET) is an promising alternative of an conventional CMOS technology in future. improvement in integration densities in past few years is remarkable but aggressive scaling of these MOS devices reaching to its limit. so the CNT replaces the isilicon so the CNTFET replaces the MOSFETs. 

Stanford university made an CNTFET model which we are using here. The codes are same as for MOSFET but the parameters need to be change like here Dcnt (diameter) of the CNT plays a role like L in the MOSFET.

SETUP: First we need to setup the the tools for CNTFET.
  • Install the HSPICE in your system 
  • download the library of CNTFET from standford university website. or CLICK HERE
  • make a directory with the name of project and paste all the file in the project from the package you downloaded from stanford university
WRITE THE CODE: Now write the code for the circuit in my case i am writing a code for an inverter.

*For optimal accuracy, convergence, and runtime
.options POST
.options AUTOSTOP
.options INGOLD=2     DCON=1
.options GSHUNT=1e-12 RMIN=1e-15
.options ABSTOL=1e-5  ABSVDC=1e-4
.options RELTOL=1e-2  RELVDC=1e-2
.options NUMDGT=4     PIVOT=13

.param   TEMP=27

*Include relevant model files
.lib 'CNFET.lib' CNFET
*Some CNFET parameters:

.param Ccsd=0      CoupleRatio=0
.param m_cnt=1     Efo=0.6    
.param Wg=0        Cb=40e-12
.param Lg=32e-9    Lgef=100e-9
.param Vfn=0       Vfp=0
.param m=19        n=0       
.param Hox=4e-9    Kox=16

* Define power supply

*Vdd     1     0     0.9

* Main Circuits
* nFET

X2 Out N_1 Gnd Gnd NCNFET Lch=Lg  Lgeff='Lgef' Lss=32e-9  Ldd=32e-9 
+ Kgate='Kox' Tox='Hox' Csub='Cb' Vfbn='Vfn' Dout=1  Sout=0  Pitch=20e-9  n1=m  n2=n  tubes=3

* pFET

X1 Out N_1 Vdd Vdd PCNFET Lch=Lg  Lgeff='Lgef' Lss=32e-9  Ldd=32e-9 
+ Kgate='Kox' Tox='Hox' Csub='Cb' Vfbp='Vfp' Dout=1  Sout=0  Pitch=20e-9  n1=m  n2=n  tubes=3

VVoltageSource_1 Vdd Gnd  DC 0.9
VVoltageSource_2 N_1 Gnd  PULSE(0 0.9 0n 5n 5n 50n 100n)


.tran 1n 500n

.MEASURE avg_pow AVG power FROM=1n TO=500n

.MEASURE TRAN t1 TRIG V(N_1) VAL = 0.45 TD = 0n RISE = 1
+ TARG V(Out) VAL = 0.45 FALL = 1

.MEASURE TRAN t2 TRIG V(N_1) VAL = 0.45 TD = 0n FALL = 1
+ TARG V(Out) VAL = 0.45 RISE = 1

.MEASURE TRAN tp PARAM='(t1+t2)/2.0'

Now after writing the code save it with the extension "your_file_name.sp".

HSPICE : Now lets start to simulate your design with HSPICE.

1) Open the HSPICEpui

2) Click the OPEN Button to open the design file or the code file you wrote. Browse your design file in the design section and left rest of the thing.

3) Now click the Simulate button .

4) Now open the 'Avanwaves' to view your pulses or the output.

5) Now click the operating points you want to view like in my case i double click on vin and vout.
and  see the wave form.

6) Now click on the Editll to view your result like Power , Propagation Delay , Hold Time etc.

As you can read that the average power(avg_power) is .17 microwatt and propagation delay(tp) is about .18 ps.

                                           Clean India
Please share and comment if you see this tutorial informative

About the Author

Vikas Sharma

Author & Editor

Hobbyst Researcher and working in electronics domain, M.Tech in VLSI Design and Embedded Systems.


  1. Thanks for sharing your view to our knowledge’s, its helps me plenty keep sharing…
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  2. Nice blog, here I had an opportunity to learn something new in my interested domain. I have an expectation about your future post so please keep updates.
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  3. Pretty article! I found some useful information in your blog, it was awesome to read, thanks for sharing this great content to my vision, keep sharing.
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  4. the code is working but for whatever value of capacitor the output is same

  5. sir,please provide the link for downloading hspice software

  6. can we change stanford model libraries like changing tox,dia etc..for 32nm technology

  7. Superb i really enjoyed very much with this article here. Really its a amazing article i had ever read. I hope it will help a lot for all. Thank you so much for this amazing posts and please keep update like this excellent article.

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  8. Show how to measure gain and bandwidth of analog circuits like cntfet Differential amplifier in hspice Code

  9. Is the HSPICE code dependent upon the library file? Also, needed some help in implementing a NAND gate using CNFET

  10. Hi. I have a proble with the library. It does not have the parameter Ctot*Wgate and it can not run and produces error. can you help me?

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