Power MOSFET versus BJT – loss characteristics Compared to a bipolar junction transistor (BJT), a power MOSFET generally exhibits which combination of switching and conduction losses (for similar voltage/current ratings)?

Introduction / Context:
Selecting between MOSFETs and BJTs hinges on their dynamic and static loss mechanisms. BJTs are current-driven devices with charge storage; MOSFETs are voltage-driven with resistive conduction paths characterized by Rds_on.

Given Data / Assumptions:

• Similar voltage and current range.
• Hard-switched applications.
• Room-temperature comparisons (Rds_on increases with temperature).

Concept / Approach:

MOSFETs switch faster with negligible charge storage tail, leading to lower switching losses. However, conduction loss is I^2Rds_on, which can exceed BJT conduction loss (≈ IVce(sat)) in some ranges, especially at higher currents or elevated temperatures.

Step-by-Step Solution:

Verification / Alternative check:

Loss curves in datasheets show MOSFET superiority at high frequency, while BJTs can be advantageous for conduction at certain currents if switching frequency is low.

Why Other Options Are Wrong:

• Higher switching losses for MOSFET are generally untrue.
• Lower conduction losses for MOSFET are not typical at high current unless Rds_on is very low.
• Both lower is unrealistic across wide ranges.

Common Pitfalls:

Ignoring temperature rise on Rds_on; not accounting for gate charge in driver design, which affects efficiency but not conduction loss directly.

Final Answer:

lower switching losses and higher conduction losses