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1  Simulators / AMS Simulators / Re: ams simulator vs psectre simulator for ams simulation
 on: Yesterday at 1:45pm 
Started by AMS_ei | Post by Ken Kundert
Of course. It is the same information, just in a different format.


2  Design / Analog Design / ADC layout
 on: Apr 22nd, 2017, 11:43pm 
Started by skyer | Post by skyer
Hi all:

Now, I need to start my ADC's layout, but I haven't drawn any kinds  of layout at all. Is there anyone can offer some help, such as some learning materials, that will help me a lot!
THX in advance Smiley

3  Design / Analog Design / SC-CMFB for MDAC
 on: Apr 22nd, 2017, 2:39pm 
Started by designerH | Post by designerH
Dear all,

I would like to ask you about the biasing of an MDAC residue amplifier.
The topology of the amplifier is depicted in the figure, attached to this post. As understood, CMFB sets the output voltage.

This is the fact that any mismatch will diminish the DC output voltage even a SC-CMFB is utilized, and one output will go up and other will go down. How can the amplifier be designed robust against process variations?

I hope to receive your comments.

4  Modeling / Semiconductor Devices / Spectre to LTspice conversion
 on: Apr 22nd, 2017, 7:16am 
Started by Daves0402 | Post by Daves0402
Hi friends,

I have designed a chip with Cadence Virtuoso and I will use this device to design another product. In this product there'll be a lot of commercial devices (Most of them are Linear Devices products) . If  I could use a simulator like LTSpice it would be Ok since I can get the commercial models on the web and simulate them.

So I need to export MY device to LTspice environment from spectre environment.

I can't find any help to do this till now.

Could you please help me?


5  Simulators / AMS Simulators / Re: ams simulator vs spectre simulator for ams simulation
 on: Apr 21st, 2017, 8:32pm 
Started by AMS_ei | Post by AMS_ei

Thank you, Andrew and Ken for your valuable inputs.
I have one doubt here.
If I run stand alone Spectre on any analog design, it generates the netlist in .scs format and then run on it.

If I run AMS simulator on any analog design, it generates netlist in .vams format and then run on it.

Did you mean that running a simulation on .vams netlist (AMS simulator) and on .scs netlist (for standalone spectre) will give the same results in accuracy?

Thank you.

Kind regards.

6  Simulators / AMS Simulators / Re: ams simulator vs psectre simulator for ams simulation
 on: Apr 21st, 2017, 8:04pm 
Started by AMS_ei | Post by Ken Kundert
Some people wonder if AMS Designer is less accurate than Spectre. It is not. AMS Designer employs Spectre underneath, so you can expect similar behavior and accuracy.

If you system is entirely analog, then Andrew is right, using Spectre is generally best. It is a cheaper license, and you get a much wider palette of analysis choices (AMS Designer is largely constrained to transient analysis).

However, if you are simulating a mixed-signal system, it is generally much easier to write mixed-signal models in Verilog-AMS, and they can run much faster.


7  Simulators / AMS Simulators / Re: ams simulator vs spectre simulator for ams simulation
 on: Apr 21st, 2017, 1:51pm 
Started by AMS_ei | Post by Andrew Beckett
Well, the main benefit of using AMS is if you have some digital behaviour in there somewhere - then you can take advantage of the event-driven engine in AMS to improve performance. If everything is at transistor level (or you just have verilog-a models) there is no benefit in using AMS as the simulator - you have a bit more overhead and it costs you more in terms of licenses. In other words, if everything is analog, using a circuit simulator is probably a better choice...

8  Simulators / Circuit Simulators / Re: Stability analysis of a continuous time CMFB
 on: Apr 21st, 2017, 1:44pm 
Started by polyam | Post by Andrew Beckett

It's just back to back baluns (if my memory is correct) and then the choice on the ADE stb analysis from controls whether you are analysing the differential mode or common mode stability by picking the appropriate iprobe.

The earlier cmdmprobe (which wasn't encrypted) was inaccurate - you're right, but diffstbprobe should always have been OK, AFAIK.

Not entirely sure why we encrypted it - that seems more trouble than it's probably worth...



9  Analog Verification / Analog Performance Verification / Re: dynamic comparator noise measurement.
 on: Apr 21st, 2017, 1:36pm 
Started by yvkrishna | Post by Andrew Beckett
yvkrishna wrote on Mar 16th, 2017, 8:22pm:
So this would be in a 2 step, first give only few (~100) sidebands to get a crude estimate for flicker noise corner at the output of the comaparator and then use that to get the correct estimate for sidebands in the next iterations (??)

No, it's not in two steps. I didn't say that... it doesn't work the way you are suggesting.

Did you try it?


10  Analog Verification / Analog Functional Verification / Re: creating compile time define switch in .scs file
 on: Apr 21st, 2017, 1:32pm 
Started by AMS_ei | Post by Andrew Beckett
Yes. Use the cpp (C pre-processor) directives #ifdef, #ifndef etc, and then run "spectre -Dvar" or "spectre -Dvar=val" to define them on the command line. You can also just run "spectre -E" to invoke with the C preprocessor first, which happens if you pass -D too.  More on cpp can be found in "man cpp".


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