Hassan, I wondered if that might be the thing to do. It's also possible in simulation (and indeed, frequent practice), to add the resistor I suggested to set a DC level. In simulation it would be a very large value, such as 1 to 10Meg. It should do the trick in at most a couple of cycles. This is another way of implementing Kumar's suggestion of setting the initial charge condition on the cap. Also note that this effect is not necessarily a "simulation thing" - there is some relationship to reality. If you have a cyclical signal, like a clock, you should indeed get a 0 V DC level. But if it is data, a long string of "1"s or "0"s will shift the DC level up or down. Even with a clock, a duty cycle that is not exactly 50% can have a small offset. Try a 45% duty cycle in your simulation and you'll see what I mean! Alan Hilton-Nickel Transmeta Corp. Hassan Ali wrote: > > Thanks all for your suggestions. > > Actually, the sure way is that suggested by Lou - to run the simulation to > death! > Actually, in my case I had to run it for 2500 cycles! > > Kumar's trick is interesting. I tried it but it didn't really solve the > problem. I still > had to run the simulation for a long time to obtain 0V DC. I appended the > "gsw 1 2 .." > line (only one line) in the ESpice model of the capacitor. > > Thanks again all for the support. > > Regards. > > Hassan. > > On Mar 13, "C. Kumar" <kumarchi@xxxxxxxxx> wrote: > > > > try this. > > > > cdc 1 2 my_dccap > > gsw 1 2 i='if (time <= 0) (1e3 * v(1,2)) else 0' > > > > Patrick_Carrier@xxxxxxxx wrote: > > I agree with Lou. I know in Spice you can get around that anomaly by > > specifying an initial charge condition on the cap. I don't think there is a > > way to do that in Specctraquest though, so you need to just wait several > > cycles to look at the waveform. > > > > --Pat > > > > -----Original Message----- > > From: Sanchez, Louis [mailto:louis.sanchez@xxxxxxxxx] > > Sent: Wednesday, March 13, 2002 10:55 AM > > To: 'hassan@xxxxxxxx'; si-list@xxxxxxxxxxxxx > > Subject: [SI-LIST] Re: SPECCTRAQuest: DC level shift with series caps > > > > > > > > Hello Hassan............ > > > > It will take several pulses before you see the expected results in an AC > > coupled network. I believe that you are dealing with the initial condition > > of time it takes for all storage elements (capacitors) to reach equilibrium. > > I suggest that you lengthen the period of your analysis in the Preferences > > section of SigXplorer. > > > > Lou A. Sanchez > > > > -----Original Message----- > > From: Hassan O. Ali [mailto:hassan@xxxxxxxx] > > Sent: Wednesday, March 13, 2002 6:49 AM > > To: si-list@xxxxxxxxxxxxx > > Subject: [SI-LIST] SPECCTRAQuest: DC level shift with series caps > > > > > > > > Hi All, > > > > I'm trying to use SigXplorer to simulate a link with a differential > > driver and series DC-blocking caps. Contrary to expectations, > > single-ended P and N outputs measured at the load are not centered > > around 0V DC, instead each one is given a separate DC shift. When I > > remove the series caps, the output is as expected - centered around 0V > > DC. > > > > Does anybody know what I can do to have the correct single-ended outputs > > with the series caps? > > > > Thanks. > > > > Hassan. > > ------------------------------------------------------------------ > > To unsubscribe from si-list: > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > > or to administer your membership from a web page, go to: > > <a > href='//www.freelists.org/webpage/si-list'>//www.freelists.org/webpage/si-list</a> > > > > For help: > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > List archives are viewable at: > > <a > href='//www.freelists.org/archives/si-list'>//www.freelists.org/archives/si-list</a> > > or at our remote archives: > > <a > href='http://groups.yahoo.com/group/si-list/messages'>http://groups.yahoo.com/group/si-list/messages</a> > > Old (prior to June 6, 2001) list archives are viewable at: > > <a href='http://www.qsl.net/wb6tpu'>http://www.qsl.net/wb6tpu</a> > > > > ------------------------------------------------------------------ > > To unsubscribe from si-list: > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > > or to administer your membership from a web page, go to: > > <a > href='//www.freelists.org/webpage/si-list'>//www.freelists.org/webpage/si-list</a> > > > > For help: > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > List archives are viewable at: > > <a > href='//www.freelists.org/archives/si-list'>//www.freelists.org/archives/si-list</a> > > or at our remote archives: > > <a > href='http://groups.yahoo.com/group/si-list/messages'>http://groups.yahoo.com/group/si-list/messages</a> > > Old (prior to June 6, 2001) list archives are viewable at: > > <a href='http://www.qsl.net/wb6tpu'>http://www.qsl.net/wb6tpu</a> > > > > > > ------------------------------------------------------------------ > > To unsubscribe from si-list: > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > > or to administer your membership from a web page, go to: > > <a > href='//www.freelists.org/webpage/si-list'>//www.freelists.org/webpage/si-list</a> > > > > For help: > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > List archives are viewable at: > > <a > href='//www.freelists.org/archives/si-list'>//www.freelists.org/archives/si-list</a> > > or at our remote archives: > > <a > href='http://groups.yahoo.com/group/si-list/messages'>http://groups.yahoo.com/group/si-list/messages</a> > > Old (prior to June 6, 2001) list archives are viewable at: > > <a href='http://www.qsl.net/wb6tpu'>http://www.qsl.net/wb6tpu</a> > > > > > > > > > > --------------------------------- > > Do You Yahoo!? > > Try FREE Yahoo! Mail - the world's greatest free email! > > <P> try this. > > <P> > > <P>cdc 1 2 my_dccap > > <P>gsw 1 2 i='if (time <= 0) (1e3 * v(1,2)) else 0' > > <P> > > <P> <B><I>Patrick_Carrier@xxxxxxxx</I></B> wrote: > > <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: > > #1010ff 2px > solid"><BR>I agree with Lou. I know in Spice you can get around that anomaly > by<BR>specifying an initial charge condition on the cap. I don't think there > is a<BR>way > to do that in Specctraquest though, so you need to just wait > several<BR>cycles to look at > the waveform.<BR><BR>--Pat<BR><BR>-----Original Message-----<BR>From: > Sanchez, Louis > [mailto:louis.sanchez@xxxxxxxxx]<BR>Sent: Wednesday, March 13, 2002 10:55 > AM<BR>To: > 'hassan@xxxxxxxx'; si-list@xxxxxxxxxxxxx<BR>Subject: [SI-LIST] Re: > SPECCTRAQuest: DC level > shift with series caps<BR><BR><BR><BR>Hello Hassan............<BR><BR>It will > take several > pulses before you see the expected results in an AC<BR>coupled network. I > believe that you > are dealing with the initial condition<BR>of time it takes for all storage > elements > (capacitors) to reach equilibrium.<BR>I suggest that you lengthen the period > of your > analysis in the Preferences<BR>section of SigXplorer.<BR><BR>Lou A. > Sanchez<BR><BR>-----Original Message-----<BR>From: Hassan O. Ali > [mailto:hassan@xxxxxxxx]<BR>Sent: Wednesday, March 13, 2002 6:49 AM<BR>To: > si-list@xxxxxxxxxxxxx<BR>Subject: [SI-LIST] SPECCTRAQuest: DC level shift > with series > caps<BR><BR><BR><BR>Hi All,<BR><BR>I'm trying to use SigXplorer to simulate a > link with a > differential<BR>driver and series DC-blocking caps. Contrary to > expectations,<BR>single-ended P and N outputs measured at the load are not > centered<BR>around 0V DC, instead each one is given a separate DC shift. When > I<BR>remove > the series caps, the output is as expected - centered around > 0V<BR>DC.<BR><BR>Does anybody > know what I can do to have the correct single-ended outputs<BR>with the series > caps?<BR><BR>Thanks.<BR><BR>Hassan.<BR>------------------------------------------------------------------<BR>To > unsubscribe from si-list:<BR>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' > in the > Subject field<BR><BR>or to administer your membership from a web page, go > to:<BR><a > href='//www.freelists.org/webpage/si-list<BR><BR>For'>//www.freelists.org/webpage/si-list<BR><BR>For</a> > help:<BR>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject > field<BR><BR>List > archives are viewable at: <BR><a > href='//www.freelists.org/archives/si-list<BR>or'>//www.freelists.org/archives/si-list<BR>or</a> > at our remote archives:<BR><a > href='http://groups.yahoo.com/group/si-list/messages'>http://groups.yahoo.com/group/si-list/messages</a> > <BR>Old (prior to June 6, 2001) list archives are viewable at:<BR><a > href='http://www.qsl.net/wb6tpu<BR><BR>------------------------------------------------------------------<BR>To'>http://www.qsl.net/wb6tpu<BR><BR>------------------------------------------------------------------<BR>To</a> > unsubscribe from si-list:<BR>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' > in the > Subject field<BR><BR>or to administer your membership from a web page, go > to:<BR><a > href='//www.freelists.org/webpage/si-list<BR><BR>For'>//www.freelists.org/webpage/si-list<BR><BR>For</a> > help:<BR>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject > field<BR><BR>List > archives are viewable at: <BR><a > href='//www.freelists.org/archives/si-list<BR>or'>//www.freelists.org/archives/si-list<BR>or</a> > at our remote archives:<BR><a > href='http://groups.yahoo.com/group/si-list/messages'>http://groups.yahoo.com/group/si-list/messages</a> > <BR>Old (prior to June 6, 2001) list archives are viewable at:<BR><a > href='http://www.qsl.net/wb6tpu<BR><BR><BR>------------------------------------------------------------------<BR>To'>http://www.qsl.net/wb6tpu<BR><BR><BR>------------------------------------------------------------------<BR>To</a> > unsubscribe from si-list:<BR>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' > in the > Subject field<BR><BR>or to administer your membership from a web page, go > to:<BR><a > href='//www.freelists.org/webpage/si-list<BR><BR>For'>//www.freelists.org/webpage/si-list<BR><BR>For</a> > help:<BR>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject > field<BR><BR>List > archives are viewable at: <BR><a > href='//www.freelists.org/archives/si-list<BR>or'>//www.freelists.org/archives/si-list<BR>or</a> > at our remote archives:<BR><a > href='http://groups.yahoo.com/group/si-list/messages'>http://groups.yahoo.com/group/si-list/messages</a> > <BR>Old (prior to June 6, 2001) list archives are viewable at:<BR><a > href='http://www.qsl.net/wb6tpu<BR><BR></BLOCKQUOTE><p><br><hr'>http://www.qsl.net/wb6tpu<BR><BR></BLOCKQUOTE><p><br><hr</a> > size=1><b>Do You Yahoo!?</b><br> > > Try FREE <a href="$rd_url/tag/<a > href='http://mail.yahoo.com/";>Yahoo!'>http://mail.yahoo.com/";>Yahoo!</a> > Mail</a> - the > world's greatest free email! > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu