2N3904
The 2N3904 is a common NPN bipolar junction transistor used for general-purpose low-power amplifying or switching applications. It is designed for low current and power, medium voltage, and can operate at moderately high speeds. Overview. The type was registered by Motorola Semiconductor in the mid-1960s, together with the complementary PNP type 2N3906, and represented a significant performance/cost improvement, with the plastic TO-92 case replacing metal cans. This transistor is low-cost, widely available and sufficiently robust to be of use by experimenters and electronics hobbyists. 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. Some manufacturers mark "EBC" on the molded part, but all are required to have those connections for a part which is a "2N3904". It is a 200 mA, 40 V, 625 mW transistor with a transition frequency of 300 MHz, with a minimal beta, or current gain, of 100 at a collector current of 10 mA. Related parts. 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. The complementary PNP transistor is 2N3906. Part numbers. The 2N3904 (NPN) and 2N3906 (PNP) are complementary transistor pairs. These transistors are available in package styles TO-92, SOT23, SOT223 with different prefixes.