The SMBJ40A is a bi-directional transient voltage suppressor (TVS) diode manufactured by Littelfuse. It is designed to protect sensitive electronics from voltage spikes caused by electrostatic discharge (ESD), lightning, and other high-voltage electrical transients. The diode is rated to absorb up to 40A of direct or alternate current, with a peak pulse power of 600W. It is available in an industry-standard DO-214AB package. The device features a low stand-off voltage of 4V and a max clamping voltage of ±23.8V. The SMBJ40A is a popular choice for automotive, telecom, and industrial applications.