The 1SMA4749A-749A is a series of SMA Zener Diodes that is RoHS compliant and manufactured by ShunYe. They are designed to protect circuits from over-voltage conditions and maintain a constant output voltage. They feature a low dynamic impedance, fast switching times, and low noise levels. They also feature a variety of applications, such as temperature, voltage, and current control in automotive, industrial, and other equipment. These devices offer superior performance and reliability in the harshest environments, making them perfect for applications where high quality and long life are required.