The BC549A is a low-power, NPN, bipolar junction transistor manufactured by Diotec. It is mainly used for amplification and switching purposes. This transistor has several characteristics, such as low collector-base voltages, a low current gain cutoff frequency, and a high breakdown voltage. Its collector current rating is 100 mA, its power dissipation is 625mW, its hfe is 300-500, and its collector-emitter voltage rating is 40V. This transistor is often used in signal amplifiers, low noise amplifiers, current regulator circuits, and switching circuits.