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Simulators >> Circuit Simulators >> analysis based switch (sp1tswitch) in Spectre
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Message started by vivkr on Jan 16^th, 2008, 12:03am

Title: analysis based switch (sp1tswitch) in Spectre
Post by vivkr on Jan 16^th, 2008, 12:03am

The analysis based switch sp1tswitch from Spectre analogLib can be configured to be closed or open for DC, AC, TRAN and IC.
Is it possible to do something similar for other analyses such as STB etc.?

Thanks
Vivek

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by achim.graupner on Jan 16^th, 2008, 2:24am

Hello,

well stb is an ac analysis, thus the switch behaves as in ac.
Notice that the instance named in stb (iprobe, vdc) is closed during dc but opened during ac (like a tp1switch)

Regards,
Achim

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by vivkr on Jan 16^th, 2008, 7:39am

Hello Achim,

My question was more general. So you are saying that AC switch levels will also work
for STB and XF. In some ways, that's not so desirable. What about NOISE? Also AC?
What about PSS? From what you mention, I would suppose that all these would also
be configured as AC as one would normally do a PAC, PNOISE etc. after PSS.

Is there a good way to get around this and build a switch which can be custom closed
for a given analysis, like sp1tswitch?

Regards
Vivek

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by Frank Wiedmann on Jan 16^th, 2008, 8:39am

You might be able to use the analysis() function of Verilog-A for writing the code for such a switch. See the Verilog-A Language Reference for details.

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by haykp on Nov 2^nd, 2010, 4:22am

Hi Folks,

Sorry for my late replay...

To be honest I couldn't clear understand what is the reason of using sp1tswitch cell. So this is some cell which based on analyze type either opens or closes.
I don't understand why to use such cell ...

Please could you elaborate more why you need to use such cells or a good doc would be very helpful.

Thanks in advance.

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by sheldon on Nov 2^nd, 2010, 6:36am

Haykp,

The switches are most often used in testbenches. For example, if
you want to measure open loop gain. You can short the inverting input
and the output for the dc operating point calculation so the circuit has
a well defined operating point. Then open the switch for ac analysis
to measure open loop gain.

Best Regards,

Sheldon

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by haykp on Nov 2^nd, 2010, 8:40am

Hi Sheldon,

Many thanks for your feedback.

Could you please elaborate also about the instantiation of these switches. So are these switches hspice cells or verilogA cells. How you simulate them? What is their implementation looks like.
the issue that I am facing is following: I need to use that cells in my design, but I don't know how I can do that ( sorry cannot tell more).

Title: Re: analysis based switch (sp1tswitch) in Spectre
Post by sheldon on Nov 2^nd, 2010, 9:39pm

Haykp,

The analysis dependent cells are Spectre primitives. They are
available in analogLib, the cell name is sp1tswitch.

Best Regards,

Sheldon