to get a mosfet very commonly available in local market

Hello sir

we have BC547,BC557,2N2222,2N2646 etc etc as BJT FET
but i need a simple mosfet number for the most common use as i do in case of above mentioned
as i found the working speed less with them so want to replace with mosfets . . please help with substitutes too , i am unable to have one :--x

Most small MOSFETs are surface mount. Power MOSFETs are available in leaded packages. No-one can guess what is available in your local store. Like you think that 2N2646 is a common device; it really isn't. It may be common where you are, but I've never used it. If you go here you can select the packages that you're comfortable with soldering, and even manufacturers if you know that some manufacturer items are more popular in your country, and then list the devices. Next, sort by price, in the hope that the lowest price devices are the most common (not always the case),
Note that you should be examining the characteristics of the MOSFETs that you want (e.g. VGS, VDS, RDS...).
I know you like "simple" but you're not going to learn anything unless you begin to examine datasheets and the circuit that you're trying to construct.
These are some that I consider common, but they are all surface mount, notice I can only find two leaded devices (other than power devices). If you can't find these, then you're looking in the wrong place. You could order these is any part
of the world, I'm sure of it.
BSS138 - Nch
BSS84 - Pch
BSS123 - Nch
FDN336 - Pch
BS270 - Nch leaded
2N7000 - Nch leaded

2n7000, BSS123, and BSS84 are all extremely common and dirt cheap. I believe 2n7000 is the fastest among the common devices, though you can certainly find faster ones if you look hard.

Hey Rajaram!

IRF series MOSFETs are easily available in market.

Typical example IRF3205: 110V,55A

ohhh thanks thanks a lot to all but i dont want simple cause i know nothing is simple but i want to make things simple so as to make electronics easy for everyone , well anyone is having idea how to replace a BC 548 with an N channel mosfet . . please comment what i ve to do next for that

I strongly suggest you study what's known as "characteristics" of devices, which are essentially curves that describe the behavior of a device when subjected to an input on one or more pins. These characteristics provide a high level description of how a device will work in a circuit with those inputs. Secondly, there are some well known circuit arrangements for performing certain tasks (amplification, switching). These too are described in books, and will help you identify circuits which are candidates for MOSFETs or for BJTs. What books can you get access to in your country?
I could recommend some, but I feel I will be wasting my time unless you actually intend to study.

ya sir i gone through so many books but didn't find any practical help , everywhere same story so please help me with any links or authors

Hm, this is in most textbooks. Which books did you read that were not of help? You should "name and shame" these books so that others don't read them.
What do you mean practical help? This is math (graphs) that you need to look at. It is fairly simple graphs however, doesn't need a math degree.
If you just want practical circuits, there are tons of websites, some with good circuit diagrams, some with bad ones, and although you can learn a little by observing them, you won't learn much until you know the behavior of the devices.
"Circuits devices and systems" by Ralph Smith has some chapters including graphs describing BJTs, MOSFETs and the calculations (and worked examples) required for use in amplifiers for instance. A very practical book with some simply described math is the Art of Electronics. No one has ever regretted reading that book, or complained that it did not contain practical info.

okk sir thanks for the info , i ll go through that , you are to explaning about some sites , so if you have any link best to your knowledge please tell

I've (and others) have already provided links to "circuits" websites to you in the past. If you're now looking to modify circuits and
replace components with other ones, it leads to the conclusion that you need to understand the behavior of devices.

Nothing is for free, so although university lecturers sometimes produce some free web-based material, it is more brief and expects
a certain amount of knowledge that you'll only find in a book. If you're serious about the topic, then expect to read a book or two.
So, get to a library. Not everything in life is available via a link. "i gone through so many books but didn't find any practical help"
implies you've not made much of an effort at all.

without proper guidence who it could be possible for me ? i asked so many lecturers & all that but same reply as per book nothing more than that , i too completed all BJT work depending on this forum & my self practicals , in acedamic sessions we just have to go thorugh what's in syllabus & what's according to examination point of view , i just today listened to you & grabbed something new but i am in a part of india where it's not possible to do what i mean to do actually but still i am trying so asking you for help . .

Ok, glad you're trying. Just wanted to be sure. I'll try to find some semi-decent web links and post them. However, it is still worth checking your local library for the recommendations from your lecturers; they may know what books are available locally, and if they are any good.

EDIT:
These links are quite good.
**broken link removed**has a few different things on it, including some basic but
quite nice interactive demos of a MOSFET and a few other devices. Also, it has information on simulation software, which may be out of date but at least it helps you know what to look for.
This electronics guide appears to have a lot of information if you follow the links for any topic, and it looks easy to understand.
There is a lot of links to PDF lecture notes here. I only looked at a few.

wowwwwwwwwww
sir just awsome it is , u helped me a lot lot lot so thankssssssssssss for all that , what i need is included here & is more than enough now let me proceed to what i want to have actually . . . .
i too ordered some mosfets as these days such devices are not available very much due to repairing work getting colapsed so i ll hv to pay 5 times more than the original rate , , , well doesn't matter i ll proceed coz . . "What i say i do & what i don't i do it definitly"
:-D:lol:

Just curious, how much is a MOSFET there? Here it is just a few pence (or cents), e.g. maybe $0.05 for a single small MOSFET (surface mount, but it is possible to hand-solder). The power MOSFETs (like IRF3205) can be much more expensive (£1.50 or more).
If you know what you want, it may be worth ordering all you need in a single go, e.g. from elsewhere in Asia, e.g. China or Singapore.

hmm i am at the centre of india & here its not easy to have FETs also but they demand a large amount cause they don't bring in whole sale as its not in demand , presently i need first three mosfets to complete the very first step , well tell me what are power mosfets & how its diffrent from simple one ?
is the speed varies in both cases ? , actually i just need simple one to make asure that the same experiments are going as it is but with high speed & low power consumptions etc etc , if it goes well as per my criteria then i ll proceed to all the remaning practicals , ll implant it in by ordering mosfet packages & ll move for the research cells etc to present my work , but before its important to have first three simple mosfets , i too tried today for this in some new places but they didn't hear about it but they told to confirm next week or any other time , let see upto what level i can proceed . . thanks for all the info .