The parallel connection of MOSFETs allows higher load currents to be handled by sharing the current between the individual switches. Because MOSFETs have a positive temperature coefficient they can be parallel without the need for source resistors.

1. Name: Mafaz Ahmed
Series and parallel connection of MOSFET:
The parallel connection of MOSFETs
allows higher load currents to be handled by sharing the current between the individual
switches. Because MOSFETs have a positive temperature coefficient they can be parallel
without the need for source resistors.
Series connection of MOSFET:
If we want to have large voltage rating then we connect the
MOSFET in series. The main problem of the series connection is unequal voltage sharing
between devices in both transient and steady-state operations, which can damages all devices.
Parallel connection of MOSFET:
For high current ratings we use parallel connection. But it
is not that much easy to just connect them, we face problems like thermal runaway we can
damage all our devices. In paralleling of power MOSFETs, two parameter variations are of major
importance,
 Drain-to-source resistance - RDSon variation for static currents sharing
 Gate threshold voltage - VGSth variation for dynamic currents sharing
Static current sharing (Thermal Runaway):
To remove the thermal runaway problem, small resistor are connected in
series with source. If one MOSFET starts to draw slightly more current than the others it heats
up and its impedance increases which results in the current through it decreasing. This small
resistor will limits and balance the current sharing.
Dynamic current sharing (Gate drive impedances):
Parallel MOSFETs should be
mounted close together so that the gate drive impedances are the same and all transistors
switch at the same time. Keeping in mind that individual Rg resistor should be connected with
each MOSFET.