The 2n3904 is a general-purpose NPN bipolar junction transistor (BJT) commonly used in electronic circuits for amplification and switching. With a maximum collector current of 200mA and a maximum power dissipation of 625mW, the 2n3904 is suitable for a wide range of low to medium power applications. It has a low noise figure and high current gain, making it ideal for audio amplification and small signal amplification. The transistor is housed in a TO-92 package, making it easy to work with and suitable for through-hole PCB mounting. Its small size and low cost make it versatile for use in a variety of electronic projects, from hobbyist experiments to professional electronic designs. With its high performance and reliability, the 2n3904 is widely used in the production of consumer electronics, industrial control systems, and telecommunications equipment.