cannot get the VTC curve of the inverter..

 Hi all,

Please refer my inverter ckt in the attachment (scematics.png). i am designing the floating Gate programmable inverter.So by panning thru a lot of IEEE papers i have been able to design this inverter.

So in my inverter i am using two capacities Cin =1pF  and Ctun=1pF. Nmos anf PMOS are of same sizes for 180nm technology.

NOTE:Ctun and Vtun is used to tunnel out the electrons that are trapped between the two gates..i.e tunneling of electrons concept

[url=http://images.elektroda.net/87_1321107590.png][img]images.elektroda.net/.../url]




see test_schematic attachment for the test ckt. Wherein Vpulse is the Vin to the inverter with v1=0v, v2=1.8v , td=0 ,tr=tf=1ns and ton=10n T=20n ,,vdc=1.8v  ,,,Vtun=5V

I have done the trans and DC analyses of the above ckt with trans of stop time of 200ns and DC for sweep range of 0 to 1.8
[url=http://images.elektroda.net/64_1321107590.png][img]images.elektroda.net/.../url]



see the attachment output for the ADE window...here you can see the trans and DC outputwaveforms ....
[url=http://images.elektroda.net/65_1321107590.png][img]images.elektroda.net/.../url]


in TRANS analysis the input is properly inverted to give the output signal ...

BUT the DC analysis fails to give the expected VTC curve of the inverter( i am getting straight line of 1.8v)..WHY??

How can i get the VTC curve ...where i am going wrong in the analysis please point it out....

Thanks in advance!!