Ceaseless Student

OK. I’m going to go through two examples. The first one is a first-order low pass Gm-C filter. I’ll just show the circuit and then we can analyze and note that it works. Then I’ll show you the cooler part - design.

We’ll write a transfer function that we want to implement. Then map that to differential equations and go from the ODEs to circuits. I think I’ll finish out 1 way of implementing the transfer function and leave the other one at the diffEQ step in case someone actually wants to try their hand at a little bit of circuit fun. I’ll put up a link to the solution too.

OK. So here’s what a 1st order Gm-C low pass filter looks like. Why is it called a Gm-C filter? Well, you know how in an R-C filter, the R and C determine the time constant (tau)? Gm is a conductance (the inverse of resistance) so it similarly sets tau.

Gm-C Low Pass Filter

The Gm comes from the OTA. Recall that an OTA outputs a current proportional to its differential input voltage? In math: I_out=G_m(V₊-V_-). Now we note that V_out=V_- and V_in=V₊ in our circuit. We also note that all of the output current has to go into the cap and that the cap follows I_out=CV’_out. We combine our equations and get CV’_out=G_m(V_in-V_out). Let’s use τ=G_m/C. S’more rearranging gets us τV’_out+V_out=V_in.

Unless you’ve taken a class that teaches it, you’ll have to trust me that you can effectively call a derivative s and all the normal rules of multiplication etc apply (a friend of mine would tell you it’s because Liebniz’s notation is a strong notation). So we go ahead and do that and get V_in/V_out=1/(τs+1) which is the canonical form of the transfer function for a first-order low pass. Nice.

Hmmm… this is being longer than I thought it would be so I’ll be splitting it up. Next time we’ll look at a second-order filter that selects for a frequency: V_in/V_out=s/(τs+1)².

So it’s been a while.

This semester is looking to be seriously busy. I’m doing enough that Outlook has me booked for 30 hours a week of scheduled stuff. Just classes and SigSys ninja meetings really. Then I have to do the work for all those 30 hours of classes and grading for SigSys and stuff… Oh! And I’ve taken up a hobby! I’m baking bread multiple times a week so that should be exciting - that tends to happen concurrently with reading for something so it doesn’t actually take that much virgin time.

Anyhow. Now that I’m busy I thought I should get back to this blog. After all, it exists to hold neat stuff that I learn and I’m currently learning lots of neat stuff.

So this semester will see some good stuff:

• Advanced digital systems: We’re making a video game console on an FPGA. I’m not sure how bloggable it’ll be, but the class is certainly cool.
• Estimation: This is an IS (independent study) I’m doing with a few other kids. It’s a lot of order of magnitude physics estimation, dimensional analysis etc. This is a lot of neat stuff that should be fun to toss here - expect to see it a disproportionate amount.
• History of Analog Circuit Design: This is what I’m doing for my OSS (Olin Self Study). I’m pretty much trying to see if I can answer the question “How the #$% did someone think of that?!”
• 6 Books that Changed the World: This class is a half semester gig where we read and analyze a book a week. Books are: The Communist Manifesto, Uncle Tom’s Cabin, Darwin, The Prince, The Art of War and a book of my choice which will likely be John Maynard Keynes’ The General Theory of Employment, Interest, and Money. I’m planning on also reading Adam Smith’s The Wealth of Nations but that might be far too optimistic. Oh well.
• Controls: Really sweet class on a really sweet subject (feedback, transfer functions etc.) that is of questionable bloggability.
• MAD VLSI2: This one probably won’t be up here much. Neat stuff, but advanced enough to need more context than I want to provide here or you, dear reader, likely want to read.
• Signals and Systems: I’m ninjaing this class with two other kids. This is neat stuff. I’ll see if I can toss up concepty stuff here while avoiding the mathy stuff.
• Intermediate DiffEQ: Yeah. Doubt this will be here ever. It’s also the next half of the semester.
• Bread: w00t!

So that’s my semester. I’m pretty excited.

So I pimped out my Firefox s’more and I wanted to show it off. So much screen real estate for holding my internets: teehee!

Here’s a link to my current userChrome.css if anyone cares for it.

<--And these are my add-ons if anyone cares about that.

For more details on my setup, check out my post on vertical tabs or just e-mail me. Or you could even talk to me in meatspace. Crazy.

In case anyone from LH ended up here, this is the vertical tab how-to I was talking about.

If you didn’t get here from lifehacker, check out my Firefox!!

As a really big Lifehacker fanboy, I don’t really recall the last time I’ve been so excited while on the internet!

Woohoo!

Woohoo!

My site is in the top 1 million Technorati ranked sites! OK. So it’s not that impressive. On the other hand, it means that I’ve passed up like 4 megan00bs. I use mega here in the SI sense. That is all.

The website for Sitemeter is slow. Wow. It is seriously slow. Well. I have the code installed, but I have a stupid picture I want gone. Soooo slow. I’ll continue writing this when the stupid page can be made to load stuff…

OK. I’m actually giving up for today. I should drill my speedreading.

One thing I did notice: Google analytics reports stuff the day after it happens. This is boring Google! I like to be able to randomly refresh and be like “w00t! two more!” Huge props to StatCounter for having this covered. FeedBurner seems to do things in batches, but I haven’t really figured out what’s going on there. This is somewhat of a tangent but in FeedBurner’s rss metrics, they have this thing called reach that’s really hot. It accounts for aggregators and stuff instead of just counting them as one subscriber - my numbers look much shinier with planet Olin added in.

Peace out.

I’ve heard that Google analytics is the best thing out there. Then again, I had trouble installing it and I’ve heard reports that it misses test visitors and stuff…

I’ve been using Statcounter. Sadly, this reputedly solid tracker gives me substantially different results from the Feedburner’s reputedly solid tracking. What’s up with that?

So I’ve decided to load my site up with stuff and see what they all say. This might hurt the load speed a bit - I apologize in advance. What do you use? Put in a little blurb in the comments and I’ll add it the arsenal aimed at my traffic.

I’ll start by reviewing the installation process for the three I’m using as of this moment:

Statcounter - Fantastic. Personalized instructions depending on what you’re using. In blogger they just have you add one html element to your layout. So easy.

FeedBurner - Solid. It tells you where you have to go and what you have to do there.

Google Analytics - says something along the lines of “add it to your template above the tag. I’m fairly sure that this isn’t where you want it; that just goes at the bottom of the blog instead of each post. I followed the instructions for FeedBurner’s placement in the template instead and Google says Analytics is properly installed on my site. This is ridiculous. Google owns Blogger. I can’t believe they enjoy shooting themselves in the foot so much.

Update: Actually, the FeedBurner instructions don’t really work. Google’s instructions do end up working but I’m still giving them badness points for being big losers. They install just like stat counter - an html element in the template.

Please pass on any tools you use for traffic analysis to make this a broader test!

So remember how I said I’d gotten 208 unique visitors to date on Tuesday? It’s more than 275 now. Blue is the unique visitor count. Check it out for the entirety of this blog’s existence:

I use StatCounter. It’s free, easy to use (add an html element to your blog) and has decent visuals. How accurate is it? I don’t know. I recently started using FeedBurner (when Google bought FB and it became easy to use with blogger) which can do some site statistics too. Hopefully comparing them will be interesting.
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Last night at around 01:00 I was doing some reading drills and had a monstrous headache. I thought “Maybe I should do an extra nap tomorrow…” At the end of the day though, I think it was a blood sugar thing. I ate some pie and felt much better and much more awake.
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Evidently the Stop & Shop on 9 is open 24 hours. I’m also told it’s closed Sunday. But seriously. 24 hours? Around here? Hooray places that are open after 20:00!
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As part of a NASA project, I’m using a PIC as a prototype circuit. I got to be all nostalgic and literally run through a good portion of the labs we did for POE. Awesome. For my money, the hardest thing to do with a PIC is get your computer to believe it’s actually plugged in.

So. I was reading a post on the Dilbert Blog. Here’s a little taste:

What if the government could give something of value to the rich in return for paying higher taxes? It would have to be something that didn’t cost the government or its citizens any real money. How about extra rights?

As I read it I’m like “Man. That’s brilliant.” It’s an interesting question because it probably hurts the rich more than it helps them; nonetheless, separating them into a higher class of citizen would probably not go over so well with the less rational minds in the nation.

In fact, it would probably also not go well with the more strongly opinionated somewhat idealistic minds either. That’s a common type of person at Olin. Then again, we also have people on the other extreme who would see this, not as unfair, but as obvious and right.

So I’m not sure who my audience is exactly, but I’m hoping for enough strongly opinionated people for a comments fight like Scott Adams always gets:

Go!

So I was going through Lifehacker and I happened upon a little blurb about Flock. Flock describes itself as a social browser. Aight, I thought.

I downloaded it, started it and found that it had a lot of shiny stuff and then Firefox as a browser. As it turns out, that’s pretty much exactly what’s up. Flock is a Mozilla based browser. The stuff it offers is a huge emphasis on rss feeds, blogging, uploading pics etc.

The blogging interface is really not worth it. I guess I could hit either of my blogs from a single place, but it opens in a new window so it might be a longcut for me (I keep both blogs open in tabs all the time). It does have a neat right click menu with a “blog this” option. This would be great if I had a quicker blog like that; however, there are Firefox extensions that do this (eg JustBlogIt).

So that was lame. Then it has this media stream thing going up top, which displays your flickr stream or equivalent from some other site. Pretty cool, but eats screen real estate. So I tried the upload functionality. This was wonderful. It was magnificent. It gave me so much control for so little effort. Oh fantastic. Auto resize (important due to the limited monthly bandwidth thing), easy naming. Really great stuff.

In short: lame browser; great flickr uploader.

When I logged into Flickr (for the first time in a long, long time. I found a message telling me that I was now one of the Olin flickr groups admins. OK. So I posted an effortless 27 pics and then added them to the Olin group (yay Flock). Here’s the pathetically lame part. This makes me the second biggest contributor (48 pics). It’s really easy guys.