Connect with us

Substitute transistors

Discussion in 'General Electronics Discussion' started by [email protected], Apr 22, 2011.

Scroll to continue with content
  1. dwester@comcast.net

    [email protected]

    6
    0
    Apr 22, 2011
    Hi! Does any one have a good list of transistors that can be used as substitutes for others I may not have. It's impossible to have on hand everything. Even a short list would help. I realize it's not a good tech practice but it is practical.
    Thanks!
     
  2. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    As you appreciate, there are thousands of different transistors in dozens of packages. You would be wise to get transistors as you want them, possibly buying a few extra to make up a stock of those you are more likely to use. If you want a list of common types, look at circuits on the internet and note the types used, for example the 2N2222 npn transistor is often used in American circuits and has the advantage that the number is easy to remember.
     
  3. dwester@comcast.net

    [email protected]

    6
    0
    Apr 22, 2011
    The double-double duce.

    Thank you for the reply. I DO have a ton of those on hand. The 2N2222.
     
  4. shrtrnd

    shrtrnd

    3,826
    527
    Jan 15, 2010
    NTE is about the most common source for semiconductor substitutes these days.
    google NTE cross reference.
     
  5. dwester@comcast.net

    [email protected]

    6
    0
    Apr 22, 2011
    Hey! Thanks again!! I took your advice (and about $30.00) and ordered a ton of some of the common ones and some specific ones that I needed for one of my projects. I thought "what the heck...I'm placing an order anyway" so it felt like Xmas when they came! I ordered through Newark.

    Now I have a question for you experts. I got tired of buying 9V batteries so I built a circuit (DC-DC) that takes the 13.5VDC from one of my power supplies and gives me 9.00VDC out. The converter schematic used a 9.1V zener and an NTE184. I wanted a little more beef so after I read the specs, I used a 3055 which handles a collector current of 15A where the NTE184 is 4A. I used it because I had it on hand and all the specs were much more beefy. My question is (now please don't laugh...I'm not as experienced as most of you) My circuit works just fine but I was wondering if I could use two idental 9.1V zeners in parallel to ensure the zener will handle increased current? For the same reason I used the 3055 NPN.
     
  6. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    You may have two similar Zener diodes but you will not have two identical diodes, they will differ very slightly and one will take more current than the other, will heat up and take more current. It is difficult to advise without knowing your circuit but you might consider keeping one diode and using the NTE184 to drive the base of the 2N3055 so that less current is needed from the Zener circuit. If the 2N3055 disipates a lot of heat, it will need a large heat sink. Alternatively you could consider a boosted voltage regulator.
     
  7. nbw

    nbw

    48
    2
    May 8, 2011
    From a very general point of view the PN100 (NPN) and PN200 (PNP) cover a wide range of basic transistor operations. They can handle a reasonable current (0.5A) too. Worth keeping a dozen of the PN100 particularly in your toolbox :)
     
  8. poor mystic

    poor mystic

    1,074
    36
    Apr 8, 2011
    I used to have a copy of "Towers International Transistor Selector" which had a lot of information in it but was not really renowned for accuracy.
    I suppose nowadays people use the wonderful web.

    I wonder if this forum could host a database of transistor types? Users could input the values they knew and the database would soon become useful to others. It would probably be a matter of people knowing where to look.
     
  9. dwester@comcast.net

    [email protected]

    6
    0
    Apr 22, 2011
    Thank you people for the replies! I like that idea of the database. I have found some (lists) online but they are (understandably) incomplete.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,853
    Jan 21, 2010
    The easy way is to look at the specs of the device in question, then use digikey to search for a similar part. Of course it takes a little longer, and you have to understand which specs are important, but that's what I do these days.
     
  11. dwester@comcast.net

    [email protected]

    6
    0
    Apr 22, 2011
    Thanks!! I finally learned to do just that. I have not had any trouble (yet) but when I choose a sub, I make sure current handling is a little higher than the one I substitute and that hfe is close. Am I pretty safe to do this?
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,853
    Jan 21, 2010
    It depends on the application.

    The transistor may be non-critical, so even a poor match may work.

    Or the circuit may depend on the gain, the VCE(sat), or some other factor (or combination).

    The skill is in determining which is important, and then using those attributes to search out a close match.

    Unless something is very critical though, finding a transistor with very similar (or better) specs is generally acceptable. Just remember though that improving one specification will lead to a penalty somewhere else, so beware of any replacement that seems a lot better, it may not be.
     
  13. dwester@comcast.net

    [email protected]

    6
    0
    Apr 22, 2011
    Thank you once again. As soon as I learn more on how to use the Forum and understand threads, I will have many questions, not just on transistors but just this topic is enough for me now. I am not lazy and I do research a lot but I enjoy the contact with people with a similar interest as I am pretty much house bound from a heart disability.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,853
    Jan 21, 2010
    No problems, feel free to ask questions as they arise.

    For a lot of simple circuits, the transistor used is non-critical. For example 2N2222 and BC548 may be exchanged in many circuits despite them having quite different specs.

    The choice (as amazing as it may sound) depends largely on which side of the Atlantic you're on.
     
  15. nbw

    nbw

    48
    2
    May 8, 2011
    On a fairly related note, there's a chap out there in Interweb-land that has done a ton of sterling work on collecting data and sheets on all kinds of ICs, diodes, and - transistors. He's recorded data like Hfe, package types, you name it.

    The link is here:

    http://www.classiccmp.org/rtellason/transistors-2n.html

    Barney Ohmart
     
    Last edited by a moderator: May 24, 2011
    FuZZ1L0G1C likes this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-