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. This transistor is a low-cost device, widely available and sufficiently robust to be of use to experimenters and electronics hobbyists.[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.[5] Some manufacturers mark "EBC" on the molded part, but all are required to have those connections for a part which is a "2N3904".[6]
It is a 200mA, 40V, 625mW transistor with a transition frequency of 300MHz,[1] with a minimum beta, or current gain, of 100 at a collector current of 10mA.
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 625milliwatts to 1watt.
Pinout of 2N3904 in TO-92 package. Top view or PCB layout view is shown in the lower right corner.
The 2N3904 (NPN) and 2N3906 (PNP) are complementary transistor pairs. These transistors are available in package styles TO-92, SOT23, SOT223 with different prefixes.
