VDSmax

VDSmax, or VDS(max), stands for the maximum drain-to-source voltage that a transistor can withstand. It corresponds to the device’s breakdown rating between the drain and source terminals and is typically specified on datasheets for MOSFETs, IGBTs, and similar switching devices. Exceeding VDSmax can cause permanent damage via avalanche breakdown or degraded junction integrity; in operation the actual safe operating voltage is the rating with an appropriate safety margin.

Manufacturers often label this parameter as BVDS, BV(DSS), or V(BR)DSS depending on device family. The rating is specified under standard test conditions (temperature, gate voltage, and leakage assumptions) and decreases with rising temperature. Temperature derating is a common consideration in design, as higher junction temperatures reduce the effective VDSmax.

Designers derate VDSmax for temperature, supply transients, and manufacturing tolerances. Typical practice is to select a device with a VDS rating significantly higher than the maximum DC operating voltage, and to include protective measures such as snubbers, clamps, or TVS diodes to handle voltage spikes. Proper layout and conditioning help limit transient overshoot that could otherwise exceed the rating.

VDSmax is distinct from VDS(on) or VDS, which denote the on-state drain-to-source voltage at a given current, and from VGS ratings, which constrain gate voltage. It is a critical parameter in power conversion, motor control, and high-voltage switching, where transient voltages can exceed nominal levels.

Common ranges span from tens of volts for low-power devices to several hundred volts and above for automotive or industrial power semiconductors (for example, 20–60 V, 120 V, 600 V).