An apparatus and method for high-voltage transient blocking employing a transient blocking unit (TBU) that has at least one depletion mode n-channel device interconnected with at least one depletion mode p-channel device such that a transient alters a bias voltage Vp of the p-channel device and a bias voltage Vn of the n-channel device in concert. Specifically, the bias voltages are altered such that the p-channel device and n-channel device mutually switch off to block the transient. The depletion mode n-channel device employs a set of cascaded low-voltage depletion mode field effect transistors (FETs) such as metal-oxide-silicon field effect transistors (MOSFETs) connected source-to-drain to achieve the desired high-voltage operation of the TBU.