Updates to Cadence/Subversion (CDSVN) scripts

Our Brazilian Friends PCS and NGJr have offered the following changes to the CDSVN package:

  • Into the file “cdsLibMgr.lib” was created the menu item “SVN Unlock Cell”
  • Into the file “svnLockCell.il” were created the procedures “svnUnlockCell” and “svnUnlockCellFormCB”
  • Inside the procedures “svnUnlockCellFormCB” and “svnUnlockCVFormCB” were made the following changes:
  • where you have: if( !(rexMatchp(“.*.svn$”, file~>readPath) || rexMatchp(“.*%”, file~>readPath))
  • was changed to: if( !(rexMatchp(“.*.svn$”, file~>readPath) || rexMatchp(” “, file~>readPath))

Behaviors observed:

  • We don´t want the files *.cd% under version control, but if for some reason they are under version control that exist the possibility to lock them or unlock them.
  • Copying a “cell” or a “view” by “Library Manager” doesn´t copy files *.cd% which is not a problem because we don´t want these files under version control.
  • The command “[user@host CDSVN]$ svn lock *” or “[user@host CDSVN/bin]$ lock directory/” locks the files *.cd%, however, the “CDSVN Unlock Cell” or “CDSVN Unlock View” does not unlock.
  • The “CDSVN Lock Cell” or “CDSVN Lock View” does not unlock the files *.cd%, however, the commands “[user@host CDSVN]$ svn unlock *” or “[user@host CDSVN/bin]$ unlock directory/” are able to unlock.
  • Copying by the command “[user@host CDSVN]$ svn copy” copies the files *.cd% only if they are already under version control. The same behavior occurs for “CDSVN Copy Cell” or “CDSVN Copy View”. This is not a problem.
  • The command “[user@host CDSVN]$ svn add”, “CDSVN Add Cell” or “CDSVN Add View” does not add files *.cd% even because this type of file is in the list of ignored files as showed below:
    [user@host /home/user/.subversion] vi config
    global-ignores = *.cd% *.cd- *.cdslck *.Cat% *.abstract.status *.abstract.messages *.inca* *inca* .cdsvmod expand.cfg% transcript_ms

    [user@host CDSVN/]vi cadence_ignores.txt

Their updated files are attached. Special thanks to PCS for coordinating this. Remember, the CDSVN scripts are licensed under GPL.


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My other blogs & plans for the future

It used to be that I’d post just about anything here. However, after a few months of posting circuit design articles, I developed a consistent readership and decided that most of you aren’t interested in my daily life and/or the tech hobbies that I might be up to. As a result, I separated my personally-centered blogs from this blog.
I just wanted to quickly mention that if anyone is interested, I have two other blogs:
Personal Blog
Tech (software/computer) Blog

Also, you’ll notice that Google Ads are prominently displayed on this blog. I wanted to recoup the hosting costs of running this blog. Unfortunately, that didn’t end up being as profitable as I thought. So, as soon as I hit $100 of ad revenue (which is the minimum to cash out of my Google AdSense account), I’ll remove the ads. I’ll essentially be eating the hosting cost (in addition to the time I’ve put into the blog).

Unless I change my mind. Which is unlikely.

Also, I might try out some more social features on the web site. If I get the time. Which is also unlikely.

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Tunable Non-Foster Match Using Switched Capacitor

Foster’s reactance theorem states that any reactance Cannot render equation. Use Firefox instead. increases as a function of frequency Cannot render equation. Use Firefox instead.. This is true of the impedance looking into an antenna, where the reactance may be a large part of the overall impedance. The task in matching the antenna (for maximum power transfer and therefore maximum SNR) is to cancel the reactance (or susceptance) and match the resistance.

Unfortunately, this can’t be done over a large range, because as Foster’s reactance theorem states, as soon as you deviate a little from your center frequency, both the inductive reactance of your antenna and the reactance of whatever you’re using to cancel it (most likely a capacitive element) both increase (go toward Cannot render equation. Use Firefox instead.). So, for every change Cannot render equation. Use Firefox instead. in frequency from the center frequency, your antenna reactance goes up by some amount Cannot render equation. Use Firefox instead., but your matching element’s reactance also goes up by some amount Cannot render equation. Use Firefox instead..

If you had a Non-Foster element, the reactance of your tuning element would go down by some amount Cannot render equation. Use Firefox instead., compensating for the increased reactance of the antenna. You would then have  a broadband (or broader) match.

Most attempts to do this have required the use of active elements (such as gyrators) so synthesis a negative impedance. However, I’m wondering if  a switched-capacitor circuit can be used to synthesize this Non-Foster reactance. Most analyses of switched-capacitor circuits show that they are synthetic resistors at frequencies far below the switching frequency. However, what does the impedance look like near the switching frequency? Read More

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Median vs Mean

I’ve been doing some statistical measurements lately (more to follow). It occurs to me that while most people measure the mean of a set of measurements, the median is more useful.

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CircuitDesign.Info: Site maintenance

Some of you may have noticed that the site was down for a day last week.

Expect a bit more down-time: I’m going to do a bit of experimentation to ensure that future down-time doesn’t happen again (improve reliability).

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Special thanks to Justin Patrin

Special thanks to Justin Patrin for his awesome ASCIIMathML plugin. From now on, equations will look nicer, like:

Cannot render equation. Use Firefox instead.

You rock, Justin! I (and my readers) thank you.

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Differential Circuits Follow-Up


You’ll notice that this post has Matt Miller listed as the author. Poojan requested Matt’s comments on his differential circuit post. Poojan was impressed with my comments enough that he decided to make it a follow-up post. So, this post is co-written by both Poojan and Matt.

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The benefits of differential circuits


From my personal blog:

I’ve been lucky enough to find myself in a team that’s intent on finding the best circuit design for a given application. This doesn’t happen often to many people, but I feel that I’ve had more than my share of this opportunity.

The conclusion is usually that we come up with some topology (let’s call it circuit X) that optimizes all the performance criteria. I walk away wanting to generalize the experience with the lesson that circuit X is the best circuit ever, and I want to use it everywhere.

Inevitably, I find that some other topology Y is better suited for some other application. There were some specific constraints or conditions on circuit X that don’t apply to circuit Y, and as a result, circuit Y is more optimal for application Y.

It is for this reason that I won’t say that differential circuits are always better than their single ended counter-part. I will say that in my experience, I’ve come across the case where the differential circuit–or, really, the differential approach–is more effective than its single-ended counterpart. However, that’s not why I’ve decided to write this post.

Unfortunately, I’ve come across several engineers that make the generalization error in the opposite direction: they state that single-ended circuits save current. I will present a counter-example that is sufficient to disprove this generalization. Keep in mind that it doesn’t prove the opposite generalization (that differential circuits are always better).

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