Inverting Sallen-Key low pass filter

Oct 05, 2015 43 Replies

As an old friend of mine (a very accomplished physical chemist) used to say,

"A physical chemist is someone who talks physics to chemists, chemistry to physicists, and baseball to other physical chemists."

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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I ended up talking electronics to all of them. My physical chemistry classe s did include thermodynamics, and it took me longer than usual - not all th at long - to get my head around that, but when both your parents have bache lors degrees in chemistry, you do hit the ground running.

My only post-doc supervisor finally made Fellow of the (British) Royal Soci ety a few moths ago, and he is a physical chemist/photochemist. As a post-d oc I built some electronics for him and his graduate students, and rather m ore after I'd moved into industry, strictly as hobby projects.

Bill Sloman, Sydney

I ended up talking electronics to all of them. My physical chemistry classes did include thermodynamics, and it took me longer than usual - not all that long - to get my head around that, but when both your parents have bachelors degrees in chemistry, you do hit the ground running.

My only post-doc supervisor finally made Fellow of the (British) Royal Society a few moths ago, and he is a physical chemist/photochemist. As a post-doc I built some electronics for him and his graduate students, and rather more after I'd moved into industry, strictly as hobby projects.

Bill Sloman, Sydney ============================================================================== My pchem classes (3 quarters my junior year) included thermodynamics, and then finished with quantum mechanics. As an undergrad I really liked lots of different things and had a hard time deciding on what to major in between chemistry, computer science, electrical engineering, and maybe optics. I finally decided that if I went to grad school as an analytical chemist I could build and work with nice instrumentation, and do all of the electronics, programming, uhv vacuum system design, etc. that I wanted, and any of it I didn't want to do I could just say "I'm a chemist, you need a ____ for that" :-), so I wound up with a double major in chemistry and computer science (took all the ee classes a comp sci major would take, just skipped a few math and physics classes or I'd of had a double degree). Between grad school and later I've gotten to do a lot of chromatography-mass spectrometry interfacing, a good bit of uhv design and construction, some ion optics work (mostly transporting ions into a superconducting magnet for trapping and analysis), a good bit of control electronics (mostly straightforward digital stuff) and programming, and I've designed and built two complete mass specs from scratch so far. First quarter of grad school I was told to take the graduate quantum mechanics and advanced graduate organic courses since they were all that were available at the time; they weren't teaching any analytical courses that quarter. The first day the prof told us that only pchem grad students ever got an A from him, the best the rest of us could hope for was a B. It took a lot of work, but I got a B+ and considered it a victory; I was very happy that that was my last pchem class :-). Anyway, enough reminiscing, back to mostly lurking and learning. ----- Regards, Carl Ijames

I can't remember the exact name of the class, but the book is Van Trees "Detection Estimation, and Modulation Theory".

In one of the homework problems it has you derive Kalman filtering from basic principles. In another, Kalman-Bucy filtering.

I still get occasional contracts to do weird stuff at the intersection of communications and metrology that I wouldn't be able to touch if it weren't for that class. In fact, I'm working on one right now.

Tim Wescott Wescott Design Services http://www.wescottdesign.com

Awesome! thanks. If I ever have any metrology/ communications problems you'll be the first one I contact. (Don't hold your breathe.)

I did see this Ladyada, Paul Horowitz video today, where he talks about AoE3.. fun stuff, Appendix I is about TV, digital TV looks like white noise compared to the old analog AM ... sad news for SETI, unless someone is trying to communicate.

George H.

Yup. I was listening to some SETI guys talking and they were all over the notion of detecting alien broadcasts because they'd be narrow band -- we only started in on narrow-band RF comms in 1915; it's only been 100 years and we're going more and more to spread spectrum.

Assuming that the little green men out there are basically like us, that's a pretty small window of time to catch them in the act.

(and for all we know, narrow band RF signals means "we're tasty and defenseless right now!" to someone out there).

Tim Wescott Wescott Design Services http://www.wescottdesign.com

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Happily, the narrow-band period of signalling tasty and defenseless seems t o have taken more than 100 years to get to anybody hungry and offensive-min ded.

Maybe some Dubbya-equivalent in a nearby star-system is arguing that we alr eady have weapons of mass-destruction, and needed to be pacified before we get bigger ones. If they can measure our atmospheric CO2 levels they will h ave already worked out that we are dangerously irresponsible.

Bill Sloman, Sydney

}snip{

Increasing CO2 levels are the only option to be able to keep feeding our growing population. ;-)

joe

Until the population crash that's going to happen when our agriculture - de pendent on specific plants carefully selected over ten thousand years of re gular interglacial weather - collapses when our plants decide they don't li ke the new climate.

10 metre higher sea levels - after the Greenland and West Antarctic ice she ets decide that they are going to slide off into the ocean in big chunks, l ike the Canadian ice sheet did at the end of the last ice age - are going t o flood every port we've got, so shipping food from places that can still g row it to places that need it may get difficult too.

I'm probably going to be dead before it gets interesting, but while your ig norance doesn't guarantee that you are young - Jamie is both elderly and il l-informed - it seems likely that you might have to cope with it.

Bill Sloman, Sydney

Personally I think that there are three possibilities:

1: We really are alone for one reason or another.

2: We're about as interesting to the ones out there as a 1st grader is to a 6th grader

3: The solar system is a designated wildlife (or maybe game) preserve.
Tim Wescott Wescott Design Services http://www.wescottdesign.com

And Slowman is insane. Don't feed the troll. ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Graduate quantum field theory (relativistic quantum mechanics). The class wasn't the very hardest, except that the guy who cajoled me into taking it in the first place bailed out after a couple of months, leaving me with no study partner. Having a wife and daughter, I needed to graduate ASAP, so I had to bail too. (He's now the beam-time czar at Brookhaven.)

A pity--it was a great class.

Cheers

Phil Hobbs

Or, as seems most likely,

  1. As expected from Einstein's causality argument, there really is no way to accomplish FTL travel, and sending an object interstellar distances on organism-relevant time scales requires converting a major fraction of its mass into energy.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

That could be.

I think if we want to better dodge mass extinction events than we can now

-- even ones not of our own creation -- we want to spread off the planet. If we could colonize an asteroid and power it from fission I'm pretty sure we could get someplace interesting on a species-relevant time scale if not an organism-relevant one, thus dodging even more mass extinction events.

Tim Wescott Wescott Design Services http://www.wescottdesign.com

4: The universe is big. Really, really, big.

True, but as we're finding out on a daily basis, there's lots of planets out there. Really, really, lots.

If nothing else, modesty would insist that we're not unique.

Tim Wescott Wescott Design Services http://www.wescottdesign.com

Heaven help us, but there's probably another Slowman out there >:-} ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Whereas you can find pond scum like Jim Thompson in any sewage farm anywhere around the world.

Bill Sloman, Sydney

My feeling is that there aren't any hard classes, just a some badly taught classes.

Some stuff - like thermodynamics and relativistic quantum mechanics - is hard to teach well, because it does require the student to learn an unusual way of looking at the problems involved, but good teachers can do it.

Egomaniac teacher go out of their way to make it hard, because they look cleverer that way.

Bill Sloman, Sydney

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