Plotting Vth

Not sure what analysis you're doing, but if you want to plot the Vth from anything other than a DC operating point, you'll need to get the simulator to save the vth. You can do this with:

save M1:vth

or

save M1:oppoint

where M1 is the name of the transistor. This would need to go into the spectre netlist - if you're using spectre from the Analog Design Environment, you can create a file called (say) "mysave.scs" with the above contents, and then include it by referencing it from Setup->Model Libraries.

Having done that, you can access the vth for whichever analysis you're using by using the Results Browser in ADE.

Regards,

Andrew.

Thanks Andrew.

I am doing transient analysis for the rectifier for very low power applications.

I want to lower the Vth of the MOS and so I want to know Vth for different aspect ratio's.

I will try the method suggested by you once I am in lab.

If no success, I will post further details.

Thanks & regards,

Shahnaz. 

Andrew,

I tried the method suggested by you. I have used four MOSes in my circuit.

So, I included all four MOSes in .scs file to save the Vth. 

Here are some of the observations and queries:

 1. When I do Transient analysis,  I opened the results browser -> tran-tran . I found only two MOSes in that list. But when I click Vth, it plotted Vth vs time.

2. I want to plot between Vth and W or L or Vth and aspect ratio (W/L) and so I chose ac analysis by sweeping variable 'w' (width of Tr). To my great surpise , I found none of the transistor list in Results Browser -> ac-ac.

Do I need to do anthing more in order to plot Vth vs W, Vth vs L and Vth vs W/L?

If so, what should be done?

Thanks in advance. 

In response to your points:

1. The chances are that you either got the names wrong, or the transistors which are missing are subckt models and so the devices are not at the level you thought they were - you will need to investigate (hard for me to tell without seeing the data)
2. I wouldn't expect to see operating point data in an ac simulation result. That's because the operating point data doesn't vary in an ac sweep normally - the ac analysis is a small-signal analysis around an operating point, and it's the operating point which will vary. You'd have to do a dc operating point or a dc sweep to see the effect.

Regards,

Andrew.

This is nothing to do with SKILL or OCEAN. I explained how to do it with an include file in this post (just read further up - it's pretty clearly described what you have to do). Also in this recent thread there's a discussion how recent improvements to the ADE UI also allow you to do this without an include file (you need to be using IC616 ISR10 (6.1.6.500.10) or later).

Regards,

Andrew