Semiconductor The ROHM Semiconductor PTZTE253.9B is a Zener Diode that is rated at 3.9V and 40mA. This part is engineered to meet the highest standards in the industry and features a small package size. It is ideal for circuit protection, voltage regulation, and stabilization applications. The PTZTE253.9B is manufactured by ROHM Semiconductor, a global leader in semiconductor components. It offers superior reliability and performance in a wide variety of applications and is available in a range of package sizes.