If I have a non-inverting amplifier, the gain is normally 1+Rf/R1.
So if I had 9k for Rf and 1k for R1, the gain would be 10.
Now how do I calculate it if I put a capacitor with an equal Xc value to R1
in series with R1????
I thought I just calculate Xc, add it to R1. Then I would divide Rf by that
answer. But it doesn't seem to be the case, my gain is higher. I'm using
18k for Rf, 2k for R1, 5uF for C1 and 17Hz input. At 17Hz, my gain is 7.3.
Can someone shed some light on this?? I've spent a few hours on this
problem and I don't know what to search for because I don't know what this
type of circuit is called.
thanks in advance!
I'm running a computer simulation. I got the answer in the next message,
but I'm trying to understand polar cordinates right now, so the answer is a
bit confusing for me. But the gain he calculated is correct.
a
j being the square root of negative one used to be terribly important to me
but then I read the Hitchhikers Guide to the Galaxy. Now I'm even more
confused but happier :)
if you really want to have some fun run down to radio shack and get a few
741's and a variety pack of resisters and caps. you will discover you have
to use standard values for parts. resistors have a 5% tolerance (or worse)
electrolytic have a 20% tolerance (if they are new). your meter probes load
the circuit and affect the measurement.
but its ever so much fun to make something that actually does something :)
Gee, Tim, when was the last time you bought any parts? 1% is common
for resistors today, and .1% is gaining popularity. 1% SMD capacitors
are also showing up in more equipment. 741? That's the poster child
for how not to make an op-amp. ;-)
few
have
worse)
load
:)
gold band is still what i see most of in axial lead resistors.
1% SMD capacitors
the $5 multipack at the shack is easiest to come by
its real hard to plug surface mount devices into an experimenters board
741? That's the poster child
hey i started out with 709's.
to learn the "real world" as opposed to "ideal world" problems you have to
blow stuff up sometimes. get whatever is easy to come by and cheap.
sometimes you can get free "boat anchors" at hamfests and grab the parts.
I use mostly 1%, although I still have a stock of 5% & 10% from 2W
down to 1/8 W in Carbon Comp.
I don't buy parts there. If I don't already have what I need I buy
from Digi-Key, MCM or Mouser.
Not really. A couple pieces of component lead and a little solder
will take care of that, and I still have a 20,000 foot roll on the
shelf.
I didn't get my hands on an opamp until the early '70s and it was a
709. I wasn't impressed. BTW, I still have a couple tube op amps.
Take a look at my website (link is in the header) and you will see
that I have a lot of parts. The site only lists maybe 5% of what's on
hand. I still have seven work benches and a 1200 sq. ft workshop here
at home. I planned to restore old electronics when I had to retire, but
my health doesn't let me spend much time in the shop. :(
Tim, I started with used 20% resistors and 10% capacitors salvaged
from old radios and TV sets in the early '60s. When I was forced to stop
working full time (I'm 100% disabled) I was hand soldering 288 pin chips
in high end telemetry equipment as an engineering tech. As far as
scrapping true boat anchors, i prefer to rebuild them and scrap modern
garbage. I have a National NC-183R and a TS-382 on the bench right now.
Here is a link to the last electronic product I was involved with
getting to the production floor:
http://www-te.tw.l-3com.com/PDF/RCB-2000.pdf which is a dual telemetry
receiver and combiner with an optional spectrum display, all in a
compact EIA rack mount package. It was one of the first production
receivers that could handle FQPSK modulation.
I had to get the design ready to release to the production floor and
work with the Manufacturing Engineers to eliminate the bugs from their
assembly processes with the smaller SMD packages and closer lead
spacing. We had to test a half dozen different types of paste solder,
and switched to .015" Ersin solder for rework. That's not an "Ideal
world", its the real world for today's modern electronics.
what advise would you give to a young electronics student who probably
hasn't even touched a soldering iron, who is studying electronic theory and
using idealized computer simulations that will prepare him for the shock of
the real world?
alas Heathkit is no more... there are still a few kit type things you can
get if you know the right places to look.
Well, Tim, I was on the advisory board for the electronics course at
the Lake County Fl Vocational Electronics course until the head of the
school board decided it was more important to be able to build a PC than
understand how it worked. What I saw was discouraging! The students
didn't want to learn how to solder, because they had plug in
breadboards. They didn't want to use any of the test equipment because
they had "Electronic Workbench" to simulate circuits. My shop was a
half mile from the school, so I invited the kids to stop by to use my
collection of databooks as well as the work benches with real tools and
equipment they could expect to see in the real world. Only one kid did
so in all the years I was on the board. He truly had an interest in
electronics and was willing to listen and learn. He worked on some
equipment, learned to troubleshoot and wanted to know how something
worked so he could troubleshoot it without having someone watching over
his shoulder. There are a couple kids at my church that want to learn
basic electronics so I made the offer to teach them this summer. I have
a 1200 sq. ft workshop set up for RF and digital work on several work
benches and around 500,000 components in the bins so it should be
interesting. I believe in starting with the basics, then some hands
on. After that, I let them work on what they want. I keep an eye on
them, but I let them make simple mistakes. That makes them more willing
to ask questions, and to listen to the answers. I was 13 when I went to
work part time in a TV shop back in the '60s. The owner gave me a very
good piece of advice: Keep your mouth shut and your eyes and ears open,
till you have an idea what's going on, then ask questions. I've given
the same advise to the dozens of techs I've trained, since then. The
biggest failing I see in most electronics training is the failure to
teach logical thinking needed to solve a problem quickly and accurately.
As far as today's hobbyist, use the parts you can find, but learn to
use SMD parts, even if you have to tack leads on them and end up with a
ball of leads and parts in the project, as long as THEY DO SOMETHING to
learn electronics. More and more leaded parts are being dropped from
catalogs and billions of usable SMD parts are thrown away, daily. A few
good reference books, basic hand tools and a desire to learn can take
you a long way. Then its time to ask question and learn more, till you
reach the level you desire. One good book has always been the ARRL
Radio Amateur's Handbook. Millions of semiconductor data sheets are
available for free online. Download a few and have someone help you
learn to read them. Go to http:www.linear.com and download
"Switchercad" after you learn the basics to do simulations.
http://www.linear.com/designtools/softwareRegistration.jsp The author
shows up on the sci.electronics from time to time and there are a lot of
people that will help you learn to use it, or another spice package,
when you're ready. Its like working on a car. Don't be afraid to get
your hands dirty, but remember that your best tool is between your
ears. I have been an avid reader of electronics books from the seventh
grade, on. I got my hands on college texts for EEs and struggled
through the math and concepts because I couldn't find anyone to answer
any questions. By the time I took the electronics course in high school
I had more practical experience than my teacher. He made good use of
it, though. I helped the poorer students learn, if they really wanted
to. They would listen to me, because we were the same age and they knew
I was already working in electronics.
By my senior year I was designing complex tube superhetrodyne general
coverage receivers and building my own radios. I was drafted two years
out of high school and after a couple arguments over what my duty would
be I was tested for, and awarded 26T20 MOS which was a military
broadcast engineer. I was told that I was the only person to ever pass
the test at Ft Knox without spending three years of study at Ft
Monmoth, Nj. first.
It would be nice if Heathkit was still in the commercial kit
business, but they still sell educational electronic kits to schools.
http://www.heathkit.com/index.html Its my understanding that some of
the kits are only available to schools and have to be bought in
quantity, but there are dozens of small companies selling electronic
kits even though the manuals are not up to Heathkit standards.
and
of
can
Im not sure logical thinking can be tought. It may be something that just
happens by living a while.
A pale shadow of its former self. I visited the benton harbor plant in 1974.
There were women putting parts in boxes with one hand and knitting with the
other. There were numeric controlled robot "waldo" devices for moving and
stacking invantory. Rows of repair benches. In all a pretty cool operation.
so you are saying the same as me... get some real parts and see what you can
make with it. (although with much better prose)... only the vast majarity of
students only want to make the minimum effort effort to pass the tests.
In today's "Instant gratification" world, its a sad fact of life.
Too many cool electronic toys are on the shelves, and are too easy to
toss when they get tired of them. Its hard to find someone who wants to
learn it because they wanted to. The kids either saw bug money, or were
forced into by their family. One kid told me he didn't need to know how
to solder, because he was going to build robots, and was telling his
teacher that no one used an oscilloscope anymore. The teacher saw me
walking into the class and said, "He does!" and asked what I had on the
bench. At that time I had a Tektronics 350 Mhz 4 channel scope, and
described about 20 other pieces of equipment on the bench to him and the
other kids.
Most was used daily, and if I didn't use something at least one day a
week I told our in house Cal lab to give it to another tech. You should
have seen the look on the other techs faces when I was offered the first
of the new HP RF network analyzers for my bench and passed on it. Jaws
dropped as I asked another tech if he wanted it, on the condition that I
could "Borrow" it if I ever needed it. I was doing more analog and
digital at the time and he needed to align tubular filters so he would
use it several days a week and it tripled his output.
Several of the EEs at Microdyne wanted to know why I was working as a
tech instead of going back to school to get my degree. I told them it
was because of my health. Four years later, I'm 100% disabled. :( When
I found a problem, I dug up the data sheets, did my research and not
only told them, "We have a problem", I gave them the answer. I also
designed and built some of the test fixtures, I wrote and updated test
procedures. When engineering wrote them they were too close to the
design. Some steps were out of logical order. Descriptions were poor
because they wouldn't describe how to set up the test equipment for some
critical tests. You were supposed to "Know" what they were thinking.
When I wrote, or updated an older test procedure I would toss the proof
copy on a bench and ask one or two techs to try it that didn't normally
do that board or module to make sure I didn't miss anything. I took the
test and alignment time on some boards from 2.5 hours down to 18
minutes. I wrote software to recalculate the set of resistors for sets
of low pass Sallen Key video filters to tweak the -3 db point. Some of
the original calculations had too much ripple and there were 14, 1%
parts in the two stage filter with a 10% output spec. What I'm trying
to say is, Don't be afraid to learn new things in any area of
electronics, because you'll use it to build other skills on.
Thanks. I always felt that it was important to do good work for
whatever pay you got. I was the guy that got all the "Shit" work at
Microdyne, but it was because I wanted a challenge. I enjoyed tackling
what was considered unworkable and making it as easy to do, as
possible. Then someone else would demand that they should get "Those
easy jobs that Mike always gets!" :)
As far as passing on test equipment I didn't need: It would have been
in my way 99% of the time and it never hurts to make friends out of your
co workers. The guy I passed the network analyzer to didn't have many
friends there, but people treated him a lot better because he had the
equipment they wanted to borrow.
Visit this website. They have very good information about the tests and a
good forum. Their training material is decent.
www.ppi2pass.com
Charles Perry P.E.
Mike - tried to E you to let you know I sent the memory
parts today - but the *^%#&%$@ spam blocker wouldn't
let me, even though it worke 2 days ago. Ed
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