Parametric analysis / Variables seem to make no effect to simulation.

[BartlebyScrivener]

I am trying to perform a parametric analysis on my two stage op amp design. I want to see what happens if I change the number of gates of one of my transistors (Q6 in the circuit). I am hoping that reducing the aspect ratio, will reduce the current which in turn will increase the gain in the output stage.



However, if I set a variable, and then change it in my analog environment, or perform parametric analysis, it seems to make no effect? My design environment looks like this.



What am I doing wrong

Thanks.

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I just realised, changing the number of gates keeps the ratio the same. It's the ratio I wanted to change.

http://en.wikipedia.org/wiki/Rubber_duck_debugging

 

[kenambo]

Hi,

Didn't get your question..

Did you mean parametric analysis not running properly or Id doesn't make any effect on the circuit..

And Current is directly proportional to the gain of an amplifier..

Thanks

 

[Dominik Przyborowski]

I suppose that You try to simulate in AMS PDK (.35 or .5 um) using spectre simulator. In these PDKs the most important transistor parameter is "width strip" and sometimes it generates a problems in parametric simulations. Check if any differences exists between fixed and parametric simulations.