The 4 best transistors to keep in your parts kit

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His choices are:

  1. 2N3904 NPN Small Signal Transistor
  2. 2N3906 PNP Small Signal Transistor
  3. TIP120, Darlington Transistor
  4. FQP30N06L N-Channel Power Mosfet

The first 2 choices are obviously the best to have, but the others are subject to debate.

I remember the day I worked in the Discrete Division of National Semiconductor Inc. in the early ’90s, we have more than 3,000 part numbers for bipolar transistors alone.

Gil Amerio, our CEO and also CEO of Apple Inc. afterward, on one day, decided that National Semiconductor Inc. should go lean and we were ordered to reduce the products offering by 80% to save the operating cost.

Why there are so many part numbers in bipolar transistors?

A variation and combination of parameters

Initially, it is all about having the technical parameters to fit for the applications. Although there are few basic parameters such as Vc, Ic, Ib, Hfe, NPN/PNP, and packaging, it is so easy to have thousands of combinations.

High Hfe range can sell at a higher price.

The Hfe range of 2N3904 is from 100-300. High-end equipment demands a high Hfe range while low-end consumer products want a lower price. 2N3904A, 2N3904B, 2N3904C,… are created with a different range of Hfe and different prices to fit the market’s needs.

Japanese Dominate Consumer Electronics in the ’90s

In the early ’90s, a lot of consumer electronics were made in Japan and were using Japanese transistors with nomenclature different from the US. We have to create a list of transistors with Japanese nomenclature such as 2SAxxxx or 2SCxxxx so that we can sell as a direct replacement.

Best Selling devices

In the end, we just don’t care about the technical parameters and obsolete more than 2,500 part numbers based on historic sales. A very simple decision which kept my job!


Nowadays with the Internet, you can simply find and buy any transistor online. China has been the biggest factory for consumer electronics and there are thousands of local suppliers of parts especially transistors in China.

You don’t have to scratch your head to decide which 4 transistors should be kept on your parts kit. Simply buy them when you need or buy an assorted kit of transistors. They are so cheap in pricing and the delivery is quite fast.

The author was the global business manager of the Discrete division of National Semiconductor in Silicon Valley in the late ’80s.

You can now buy any parts any time, please visit or

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