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"Is" value, or "reverse saturation current" of a PN junction, how to get it?

Discussion in 'Datasheets, Manuals and Component Identification' started by Wollowstone, Mar 26, 2018.

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  1. Wollowstone


    Mar 26, 2018
    I am reading "Fundamentals of Microelectronics" (second edition) and while I can "compute" the theoretical value of the reverse saturation current of a PN junction, IS, knowing the doping level and the physical dimensions.
    Since that value occurs at many interesting places for a BJT, such as in the equation linking the collector current, IC, to VBE, through IS, which can determine with precision the value of the (theoretical) voltages (instead of assuming them to be, as example, 0.7 Volt of a forward biased junction ), my question is where, or probably, how do I get this value from a datasheet of a 2N2222 as example?
    Last edited: Mar 26, 2018
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    If you are designing your own semiconductor device you'll have access to this information and you can use it to calculate the expected values. This, along with other details allows you to predict the performance of the device, predicting what will appear in the datasheet (actually it's likely to be the other way around, you'll have an idea of how you want the device to perform and your design will have been created to match this desire).

    If you are the manufacturer of the device then you also have access to the information to calculate the expected values, and you can also test the device to determine how well it meets the desired specifications.

    If you are a high volume user of a semiconductor device you may have enough sway to be granted access to some information not generally available to the consumer. Alternatively, you might design your own device, again giving you access to all the information you require.

    As an end user with less access, you might try to drive the information from the datasheet, or perhaps try to reverse engineer the device itself. If it's possible to measure the parameter rather than calculate it, then measurement is probably the way to go. However, what is measurable may include other factors besides the value you're interested in.
    Wollowstone likes this.
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