Understanding Transistor 2N3904

In this post we learn the main specifications and pinout details of the NPN transistor 2N3904


The transistor 2N3904 comes under the category of NPN small signal, low power, general purpose transistor, mainly applicable for switching and for signal amplification.

It's dynamic range may include a current handling capability of more than 100mA for switching applications and a 100MHz frequency handling capacity fits with amplification purposes.

The absolute maximum ratings of this transistor may be understood from the following data:

  1. The Vceo or the maximum tolerable Collector-Emitter voltage is 4 volts.

  2. The Vcbo or the maximum tolerable voltage across collector-base is 60 volts.

  3. The maximum allowable collector to emitter or the Ic must not exceed 200mA.

Other Useful Characteristics of this device are discussed below:

  1. Maximum collector to emitter breakdown voltage for a 2N3904 transistor is 40 volts.

  2. Similarly the maximum collector to base breakdown voltage is 60 volts.

  3. The maximum base to emitter breakdown voltage is 6 volts.

  4. Minimum current required for keeping the base of the transistor activated is 50nA.

  5. Similarly the minimum amount of current required to keep the collector load switched is also 50nA

  6. The hFE or the forward current gain of the device is between 100 to 300.

  7. The minimum amount of voltage required for activating the collector is 0.2 volts, its also known as the collector-emitter saturation voltage.

  8. The minimum amount of voltage required to trigger the base of the device is 0.65 volts, its also called the case/emitter saturation voltage.

  9. The above data is quite sufficient and adequate for any electronic hobbyist for understanding the transistor 2N3904 safely and correctly.

The pin outs of the transistor 2N3904 are given in the following diagram.

2N3904 datasheet pinout, connection

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Sam said…
Dear Swagatam
I have read several of your transistor tutorials. Can your please explain all above in a complete detailed tutorial. For instance what are the above parameters, what they mean, where to use them and why? So far where ever I have read about transistors, they seems complicated or just incomplete in a sense that one site defines one thing and other sites defines some other parameters. A complete tutorial of a transistor so a newbe e can understand and utilize all important features of a transistor designing circuit himself, is yet to be seen.
Swag said…
Thanks Sam, for your keen interest.

I already have one related article posted in this blog, which you can eer to:


If you want more info included, please specify what exactly you are not able to understand, I'll make sure to update them immediately for you in the most easy to understand explanation.

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