HW3 prob 2: .MEASURE and DERIVATIVE functions
Dennis Coblentz
I was working on this week's homework last night, and I got completely
stuck on trying to figure out how to actually acquire VIL and VIH for
problem 2.a) using .MEASURE statements with the DERIVATIVE function.
I read the syntax for this kind of statement in the HSPICE manual
multiple times, and I've tried to implement it in many ways, but I
apparently have no clue how to use it. I understand how VIL and VIH
are found but I am unable to get HSPICE to do what needs to be done.
Additionally, for us to be able to graph/plot, is there a way to
assign a parameter the value of VIL and/or VIH found from the .MEASURE
+ DERIVATIVE function I'm trying to invoke? Do we need to use
any .PLOT commands in our netlists, or will the graph/plot be
something we can compose in WaveView?
Yue Lu
Hi Dennis,
You can come to my discussion today, I will talk more on how to find
the derivatives of VTC. The basic idea is to add a dummy which is
identical to the device under test but with an input offset.
If you cannot show up today, here is the slides I want to go over, you
can have a look at.
http://www.eecs.berkeley.edu/~yuelu/teaching/ee141/dis2.pdf
Thanks,
Yue
Matt Holland
There's two things I'm not understanding about this.
1) VIH and VIL are constants (at least, they are in the discussion
notes spice deck), so why would we want to view them in Wave Viewer?
2) i typed in the spice deck from the discussion notes loaded ran
hspice, loaded it in to wave view and nothing is plotted, not even a
straight line. also, shouldn't there be a .measure results section in
the hspice output file?
thanks,
mh
Yue Lu
Hi Matt,
If you pay attention to the problem setup, we basically want you to
plot VIH/VIL versus beta ratio. You are right that for each beta ratio
VIH/VIL is a constant.
The slides for discussion session only tells you how to measure VIH/
VIL for a fixed beta ratio. So you need to find different VIH/VIL
under different beta ratio then get the plot.
To do this, you can use (for example for inverter)
.PARAM beta=1
.SUBCKT inv in out vdd gnd
mp out in vdd vdd gpdk090_pmos1v w='beta*1u' l=0.09u
mn out in gnd gnd gpdk090_nmos1v w='1u' l=0.09u
.ENDS
.DC vin 0 1.2 stepSize SWEEP beta 1 4 0.1
If you are still not clear, please come to GSI's office hour on
Wednesday.
Thanks,
Yue
Bonjern
How do you actually plot the VIL/VIH values versus beta? I've swept
the values, but I can't seem to change the axes in Waveview. I can
plot all three on the same plot, but I can't change it so the x axis
correspond to the values of beta.
Yue Lu
Load ".ms0" (for DC measure) or ".mt0" (for TRAN measure) file to
waveview, on the control bar, click "Axes -> X Vriable". In the pop-up
window, deselect "Use Default X Variable".
Then go to the Output View window and right click on your beta signal,
choose "Signal xxx -> Use as X Variable" then you can set beta as the
x axis.
I hope this is clear to you.
If you are not happy using waveview, you can also load .ms0 or mt0
file with Excel/Matlab to do the plot.
Thanks,
Yue
Bonjern
Thanks for the response! However, I don't see the "Use as X Variable."
When the pop up window comes up and I deselect the "Use Default X
Variable," the box is still greyed out. I'm working from home, and I
tried both quasar and pulsar, if that information is useful at all.
Yue Lu
Since you are trying to use "beta" as x variable, you should right
click on the "beta" signal your Output View window(the left hand side
panel) and then you will see "Signal xxx" at the bottom. Click on it
you can get the "Use as X Variable" option. Hope this is clearer to
you?
Thanks,
Yue
Bonjern
Whoops, I didn't realize the window had to be up when I was choosing
the variable. Thanks! It's all clear now, hahaha.
lbagh...@gmail.com
> Thanks leila