transistor replacement

Discussion in 'General Electronics Chat' started by wmlowder, Jun 1, 2010.

  1. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    Hello, I am a college engineering student. I need a certain transistor for a circuits class, the "2SC1162". However, when I went to a local electronics place to buy it, they looked it up and gave me the "NTE373". Is this an equivalent transistor? How is it possible to tell? Thanks!
     
  2. Bychon

    Member

    Mar 12, 2010
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    Look up their datasheets and compare the important characteristics.
     
  3. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    Which characteristics are the most important? i.e. I know a 5W resistor would work in the place of a 1W resistor, but I don't know if the characteristics on a transistor are maxes or what?

    and also mine is the 1162, the datasheet you posted is the 1132
     
  4. Bychon

    Member

    Mar 12, 2010
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    I labeled the file wrong. If you'd bothered to open it, you'd know that. Now, open the files and look at the ability to withstand the applied voltage, carry the required current, have the same or better gain (amplification factor) in the replacement, survive the power required, and such as that. The "important" characteristics depend on the circuit you are installing the transistors in, and I can't guess what they are because you didn't provide the circuit.
     
  5. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    I didn't open it yet because I did not yet know what to look for. I guess my question is, are higher numbers better for the transistor I got because it means that it can withstand higher current or voltage? back to my resistor example, a 5W could replace a 1W but a 2k ohm would not replace a 1k ohm. So are all the ratings on the transistor datasheet the maximum voltages and currents? If it had a different gain wouldn't it be incompatible as a replacement?
     
  6. Damo666

    Member

    Aug 25, 2009
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    Hi. In general; higher power dissipation, higher Vce, etc are fine. The main things you need to compare, and keep an eye on are hfe(gain) and operating frequency..... Particularly at rf frequencies. What is your application buddy? Regards. Damian.
     
  7. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    I don't know what the application is yet, it's just on the parts list for a class I will be taking very soon. Maybe an application with radio? I'm not sure.
     
  8. ELECTRONERD

    Senior Member

    May 26, 2009
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    If you didn't open the attachments to begin with, how would you know what to look for anyway?

    Simply compare the specifications.
     
  9. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    Yes, of course I compared the spec sheets before I posted on this website. However, as I said I don't know enough about transistors to be able to properly compare the spec sheet. The specifications are different. Does that mean they're not compatible?
     
  10. ELECTRONERD

    Senior Member

    May 26, 2009
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    Not necessarily. Take a look at Damo666's post.

    For instance, if your transistor that needs to be replaced could only handle 5W of power, and if you found a transistor that could handle 6W of power with conditions equal to your original transistor, then you can use it as a replacement. Consider a transistor that could only handle 3W, however, then that transistor wouldn't be applicable.

    Note that all the conditions of both transistors don't have to be equal in every regard. If that was the case, why not just get the same transistor? Your simply trying to get by with another transistor that will work for your application.
     
  11. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    Damo said one of the big things to look for was the hFE... the hFE on the transistor seems to have a smaller range than the one it is replacing, from reading the datasheets. Would that make it incompatible? Also I know what you meant about the transistor being able to handle 6W, thats where I brought in my resistor example... I'm just not sure which numbers on the datasheets can be 'greater or equal to' or which have to be exactly the same?
     
  12. ELECTRONERD

    Senior Member

    May 26, 2009
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    With the hFE, or current gain, of your transistor, is usually listed as a minimum and maximum of two values. The gain of every transistor is unpredictible and varies widely with temperature. As long as your transistor replacement has a gain equal to or greater than your original transistors gain, you should be alright.
     
  13. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    Well from the datasheets, the max gain is higher on the transister that I don't have. However, the test conditions listed were different too.
     
  14. ELECTRONERD

    Senior Member

    May 26, 2009
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    I take it that the transistor you don't have is the one you refer to as the replacement? If the transistor you consider your replacement is higher than the gain of your original transistor, then your OK.
     
  15. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    No, the transistor that I have has a lower max gain than the one that I don't have
     
  16. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Same thing. If the transistor that you have has a lower gain than the one your looking for as a replacement, your OK.
     
  17. wmlowder

    Thread Starter New Member

    Jun 1, 2010
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    I hope we're understanding each other correctly. The transistor I bought has a lower max gain than the one that the parts list named. Is this OK?
     
  18. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    You should have defined that earlier. We may conclude based on those givin facts the following:

    -Transistor you bought = The transistor you consider the replacement (until you compare specs).

    - The transistor on the parts list = Your original transistor.

    Therefore, if your replacement transistor has a lower gain than that of your original transistor, you're not OK. You should find a transistor with proper specifications.
     
  19. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Things to look for:
    Voltage rating - a lower Vceo is no good
    Polarity - NPN can't replace PNP & vice versa
    Speed - an AF amp can't replace a HS switch
    Gain - the hFE can be higher, but not too much lower
    Package - A TO-92 won't replace a TO-39 because dissipations won't match, not to mention pinout.
    Function - a general purpose type like a 2N2904 or a 2N2222 is going to be easy to find a replacement for.
    Type - nothing but a Darlington can replace a Darlington

    That depends. If the one hFE is 200 and the other is 800, then likely no. If it's 400 and 450, probably yes. Sometimes close is good enough.

    Give us some idea of the application (even better, the schematic), and the guesses get better.
     
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