The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> AMS Simulators >> problem with ideal switches in Cadence
https://designers-guide.org/forum/YaBB.pl?num=1120481901

Message started by vivkr on Jul 4^th, 2005, 5:58am

Title: problem with ideal switches in Cadence
Post by vivkr on Jul 4^th, 2005, 5:58am

Hi,

I wonder if anyone has experienced a similar problem using the special
"sp1tswitch" provided with Spectre. This switch is useful if you want to configure
a netlist differently for different analysis and very useful.

However, if I have any such switch in my netlist (even one completely isolated from any net), Spectre refuses to perform a noise analysis citing a singular matrix as the source of error.

Any suggestions will be welcome.

Thanks
Vivek

Title: Re: problem with ideal switches in Cadence
Post by Ken Kundert on Jul 5^th, 2005, 3:47pm

It appears to be a bug. You should report it to Cadence.

-Ken

Title: Re: problem with ideal switches in Cadence
Post by jbdavid on Oct 2^nd, 2005, 6:25pm

that element is OK.. but I found Verilog A to be much more flexible..
for an example, there is a listing for a loop-opener in the paper below which includes an (outdated) example of its use.
"Functional Verification of a Differential Operation Amplifier"
... a fully differential current mirror opamp with n-channel input devices ... support the development of a verification script. Figure 1 Fully Differential Current Mirror Opamp with CMFB The following table ...
http://www.cadence.com/whitepapers/FVofDiffOpAmp_wp.pdf - 309.8KB

Outdated because today one would use the STABILITY analysis to look at loop gain and phase margin..

JBD

Title: Re: problem with ideal switches in Cadence
Post by Ken Kundert on Oct 2^nd, 2005, 10:55pm

It just occurs to me that if you have a switch isolated in a circuit, then it will result in a singular matrix unless both ends of the switch must have DC paths to ground.

-Ken

Title: Re: problem with ideal switches in Cadence
Post by jbdavid on Oct 3^rd, 2005, 11:28pm

sounds like bmslib sw_no would be a good alternative in that case..
jbd