
Show HN: SevenFortyFun, a transistor level op amp kit - kumarski
https://github.com/OpenAnalog/SevenFortyFun
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pasbesoin
Since I was curious enough to look: From the associated web site:

 _Analog has sort of kind of taken a backseat to our digital revolution, and
the founders of O|A are upset about this. Our mission is to teach the world
about analog, reclaim the forgotten domain, bring popular ICs to transistor
level pcb kits, breadboard things, break things, care about transistor
mismatches, worry about tolerances, and sometimes ask - why the heck is my
circuit oscillating?_

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benjamincburns
For what it's worth, I think your site makes a great introduction to your
cause, but a poor introduction to your contributions to this cause. To someone
already experience in analog hardware it's easy to get the reference that
"SevenFortyFun" refers to the LM741, and why that's cool - but you probably
should reach beyond that crowd if the first half of the site is to be
believed...

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cnvogel
Yes, a small link to the LM741 would have helped. Or maybe even a blown up 1:1
pinout, such as with the discrete 555:
[http://www.evilmadscientist.com/2013/555-kit/](http://www.evilmadscientist.com/2013/555-kit/)

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krupan
A comment on hobby analog design in general. I recently got my ham radio
license and in the studying process found the arrl handbook at the local
library. This is a thick, heavy book full of information about circuits,
antennas, waves, transmission lines, transceiver design, etc. for only $50. A
college textbook like this would easily have been $200. I kind of wish I had
know about it back in college.

~~~
benjamincburns
_The Art of Electronics_ by Horowitz and Hill can be had used off of Amazon
for a similar price, and is also quite exceptional.

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analog31
I think AoE is one of the best textbooks ever. Some of the sections in my
edition (from 1983) are dated, but the basics are very well presented.

~~~
tesseract
Agreed.

The second and latest edition of H&H is from 1989. In my opinion it has aged
remarkably well. A third edition has been due out 'soon' for ages now - as of
last fall rumor had it May 2014 would be the availability date - but at this
rate it seems to be anyone's guess whether TAOCP, or Art of Electronics 3rd
ed. will be completed first. In any case my expectation is that it will be
worth the wait.

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mng2
Who is this targeted at? As it stands, the documentation requires quite a bit
of EE knowledge. If it's meant for novices, you'll probably need to define
half the terms mentioned on the first page.

The other major issue IMO is instrumentation. Sims are fine for learning, but
is the student going to have the satisfaction of characterizing GBW, slew
rate, harmonics, etc? Is a computer sound card enough, and is it robust
against beginner mistakes? That's the sort of stuff I would think about if I
were you.

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krupan
I had to do design and build almost exactly this for a lab in college (I did
computer engineering and the first two semesters of analog design were
required). It was impossible to make it work with discrete components like
this due to things like uneven heating of the components. Now, in that class
we were using a bread board and not a pcb and none of us thought to trim the
leads on the components to keep it as neat looking as this. I'm curious how
much of a difference that would make.

~~~
quarterwave
The 741 has quite a few current mirrors for bias/gain, so the bias points
would be much more sensitive to transistor parameter mismatch than to wiring
neatness. Also, discrete PNP transistors tend to be different from the lateral
PNP's in a bipolar transistor IC process.

I suppose the value in ordering such a kit is that the devices shipped are
pre-matched etc, so the hobbyist may reasonably expect a first-pass success.

The 741 is dominant-pole compensated, so even if there were wiring-related
phase shifts at high frequencies there will be no loop gain in that region to
cause instability.

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slyrus
For those of us who can only count to one, what does this thing actually do?
Or, perhaps the better question, what can one do with this kit?

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OpenAnalog
Anything from a audio amplifier (a crap one at that) to a audio filter, to a
analog buffer, a comparator, many things are possible. For more information
check out
[http://en.wikipedia.org/wiki/Operational_amplifier](http://en.wikipedia.org/wiki/Operational_amplifier)

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RachelF
Ah the lost art of analog design.

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analog31
I've often wondered if some lost arts represent niche opportunities. My
username is apt. I'm keenly interested in analog, particularly precision and
low noise circuits. I have a side business that makes a niche market product
based on an analog circuit.

At my day job, I'm one of the few people left who is capable (or maybe just
willing) to compute a formal noise budget for an analog circuit. At least in
the instrumentation business, there will always be a need to get the analog
signal from the sensor to the analog-to-digital converter with dignity. And
understanding analog issues is sometimes vital to resolving those issues using
digital processing.

~~~
danelectro
Instruments have been my life.

It would be good to find out more about your efforts.

