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  1. #1
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    transistor selection help question

    Hi,

    I have a standard 2N4401 transistor.

    a low voltage input on the Base pin.
    Emitter pin to ground.
    and a 15~20V input on the Collector pin with a load.

    I have a 500mA draw from this circuit.

    upon removing the transistor and applying the 15~20V directly to the load, I have 2A draw.

    I want as much current as possible to my load. What kind of transistor can I use?
    I need a transistor that can take high voltage input
    (up to 100-200V and let up to 5A pass through the collector)

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  2. #2
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    Re: transistor selection help question

    There are some websites which help us to select similar transistors; I have used the alltransistors.com (there are others), which you can use to make the first approach, and if you don't find anyone, it is possible to adjust some parameters from the original transistor in order to increase the options, as for example, if you find few transistors compatible with the original transistor, and if its breakdown voltage could be decreased, you change this parameter and will see much more options to replace.
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  3. #3
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    Re: transistor selection help question

    The data sheet for the 2N4401 says it should typically drop 0.75V between collector and emitter pins when passing 500mA but you need to give it 50mA base current for it to achieve that.
    However, the maximum continuous collector current for that device is 600mA so it should not be used if the load can pass 2A. You need a small power transistor.
    In general, for switching applications, aim for a base current of one tenth (0.1) times the collector current to ensure the transistor is fully conducting.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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