2N3904

The 2N3904 is a common NPN bipolar junction transistor used for general-purpose low-power amplifying or switching applications.

[1][2][3] It is designed for low current and power, medium voltage, and can operate at moderately high speeds.

The construction of the 2N3904 and 2N3906 in the 1960s represented a significant performance and cost improvement, with the plastic TO-92 case replacing metal cans.

[4] When looking at the flat side with the leads pointed downward, the three wires emerging from the bottom are connected to, from left to right, the emitter, the base and the collector.

Electrically similar devices, such as the MMBT3904, are available in a variety of small through-hole and surface-mount packages, including TO-92, SOT-23, and SOT-223, with package-dependent thermal ratings from 625 milliwatts to 1 watt.

A 2N3904 made by Motorola . The pinout from left to right is: Emitter, Base, Collector. [ 1 ]
A 2N3904 (lower left) in a TO-92 package on a breadboard
Pinout of 2N3904 in TO-92 package. Top view or PCB layout view is shown in the lower right corner.