I am trying to Optimize an Amplifier Circuit using Cadence.
I need some way to calculate threshold voltage of a transistor and use it in the Optimizer tool.
eg. I have to define an Output X , where X = Vgs(M1) - Vth(M1)
Can someone please tell me how to get the Vth(threshold voltage) for a transistor in Cadence ?
You can find the threshold voltage under the DC operating point information. But, I think that information will be useless for optimization, because the threshold voltage depends on the channel length for short channel processes (Vth is not a constant).
Actually I wouldn’t spent time on optimization, if your optimization is based on the square law model and you are using a modern CMOS process. It will be off.
No, one reason why I am using optimization is that I want the transistor to be on. And yes Vth varies , that is why I need the Vth for particular design,
Eg. For the 2nd iteration of Optimization if W = x & L = y for a transistor I want an expression that gives me Vth at this iteration .
Forget about this. Vth is a weird function of L, W etc. If you want to involve Vgs-Vth why don't you just check if Cadence has a variable for this. Something like Vth_disatance or Vov.
You can try to implement you optimization algorithm into Ocean, here you can automate the howl thing and you have the chance to grab the v_th from the operating point analysis.
Have you tried with waveform calculator (wavescan)?
In wavescan, just select "info" in "Analysis selection choices" field.
With this you can plot the 'Vth' (for detail go through cadence manual/help).