Fig. 3. MOSFET used in e-fuse application (left). In e-fuse application (during turn-on) the MOSFET passes the
linear mode operation region for a significant period of time. The SOA must be checked to verify the MOSFET can
withstand the thermal stress.
Short linear mode operation – buck converter, general switching
When the MOSFET is used as high-side switch in a buck converter for example it also enters linear mode operation
for a very short period of time. Linear mode operation starts exactly when the MOSFET’s VGS voltage is at the
threshold voltage (VGS(th)) and ends with the drain-source voltage reaching zero. This corresponds to the end of the
Miller plateau. In other words: during the switching event the MOSFET is in linear mode operation. Modern power
MOSFETS, however, demonstrate dramatically short switching times. State of the art 25V-250V MOSFETs are
capable of switching thourgh the linear region within a few nano-seconds (