Author Topic: understanding datasheets  (Read 2246 times)

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Offline Vertigo

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understanding datasheets
« on: August 12, 2011, 08:43:40 pm »
as a newb, one of the things i am having the most trouble with is understanding data sheets.
i have studied the occult, i grow carnivorous plants and i once protested scientology, and quite frankly, this is weirder :P

you have a video about power supplies where you go into calculations for a 317 regulator (if i remember correctly)
and you explain some of the specifications.
i found this very helpful (well i think so, i haven't actually done anything with power regulators yet), and i would
love to see more of that kind of thing for other component types.
 

Offline ejeffrey

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Re: understanding datasheets
« Reply #1 on: August 12, 2011, 08:53:25 pm »
As a general rule, data sheets are really only useful if you know what parameters you are looking for -- for instance if you want to compare two similar parts or calculate the expected performance of a part in a system.  In order to use them effectively, you have to know how the part fits into a circuit, and then you can figur out what you might want to know about how that parts performance will affect the circuit as a whole.

For basic things like transistors, voltage regulators and op-amps, a good electronics book will teach you what the parameters mean.  For more specialized parts, try looking at application notes.  They will often have complete design examples, along with performance calculations based on the data sheet parameters.
 

Offline Vertigo

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Re: understanding datasheets
« Reply #2 on: August 14, 2011, 12:30:18 pm »
as a general rule, why is it everyone thinks that the way THEY learned something is the ONLY way to learn something?

anyways i am not asking for information about how to do some particular thing.
i am asking about the JARGON used in datasheets, which is NEVER used in any of the
2gb of beginner books i have on my hd.

i would like to be able to, when i am learning about say transistors, to be able to relate
the info from the book to what is in those datasheets.

like: the book will say this type of transitor will do this when it gets ##volts on the base.
however the book NEVER uses the same terminology i find in datasheets where the same thing is expressed
in the form of an acronym which is nearly identical to a shitload of other acronyms used in the datasheet.

i want to be able to read datasheets in such a way that i can actually related the info from books and tutorials
to the info in the datasheet.
and none of the beginner books and online tuts ive seen allow me to do that.

and btw the idea of me not understanding what anything means unless and untill i actually need it (but then how the F@#K would i know that unless i understand the what it is ???) for an autodidact like me is downright claustrophobic!


or to put it another way:
dave thought it was a good idea to explain power regulators in detail, i think that for the same reasons
doing the same thing with other types of components is also a good idea.

or to put it yet another way: i thought i was starting a new hobby, i didn't realize i was joining a cult...
 

alm

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Re: understanding datasheets
« Reply #3 on: August 14, 2011, 01:28:08 pm »
as a general rule, why is it everyone thinks that the way THEY learned something is the ONLY way to learn something?
Not sure who this response is aimed at, ejeffrey response seems fairly helpful to me.

anyways i am not asking for information about how to do some particular thing.
i am asking about the JARGON used in datasheets, which is NEVER used in any of the
2gb of beginner books i have on my hd.
From what I remember from reading the transistor section of the Art of Electronics, I believe I could understand most of the terms on an average transistor datasheet. Like the various typical and max. currents/voltages. Or current gain, and why this parameter isn't as helpful as you might expect. I believe it even shows typical datasheets for some components. Though I think the transition frequency fT and noise was covered in a later chapters.

i would like to be able to, when i am learning about say transistors, to be able to relate
the info from the book to what is in those datasheets.
Can you be more specific? A good textbook should for example talk about transistor saturation, and how there will only be a small voltage drop between collector and emitter. The datasheet should mention VCE(sat), which is the voltage between collector and emitter when the transistor is in saturation. It will also mention maximum voltages between the terminals and the maximum current through the collector, which are the values above which the part might release its magic smoke (every cult has its rituals). The book should describe what terms like IC or VBE stand for, and the datasheet will typically have a one line description for each term (eg. V(BR)CEO: Collector-Emittor breakdown voltage). Datasheets from some manufacturers are more helpful than others, for generic parts, feel free to compare datasheets to see if others are easier to understand. Start with a common part like a 2N3904, not some obscure specialized part.

A datasheet will also usually contain some curves, some will make more sense to beginners than others. A base-emitter voltage vs. collector current plot should agree with the one in your textbook, for examplem, and shows the issue of controlling the collector current directly with the VBE.

Bob Pease's book 'Troubleshooting Analog Circuits' has an appendix on how to read a datasheet, but I think it's not intended for beginners. Don't have the book in front of me to check, though.
 

Offline BBQdChips

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Re: understanding datasheets
« Reply #4 on: August 15, 2011, 10:24:22 pm »
as a general rule, why is it everyone thinks that the way THEY learned something is the ONLY way to learn something?
Probably cause that's the way decades of curriculum have demonstrated to be the most effective way to learn the subject.  I'm just guessing here...  Unfortunately EE isn't a topic you can just pick and choose which basics you want to learn. They sorta all interrelate. 

As to the jargon, simply googling or wikipedia searching the terms will tell you a simplified (or complicated) version of its definition.  Do a few and it won't be long  before you run out of terms you've not heard.  Probably one good evening searching terms in one transistor datasheet will yield enough knowledge you'll never have to do that again for transistors.
EEVBlog: The first forum you need a calculator to post on...
 


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