The MMBT5551 is a PNP transistor manufactured by High Diode. It is a Surface-Mounted Device (SMD) in a SOT-23 package that is compliant with RoHS standards. It is an NPN transistor that is commonly used as an amplifier or an interface switch in discrete or small-signal applications. This transistor has a low-power dissipation and excellent switching features. It comes with a wide variety of features, such as a high-speed switching, low saturation voltage, and good isolation voltage. The MMBT5551 is suitable for a wide range of applications, such as switching, general-purpose amplification, inverter circuits, and electronic control systems.