1. Current and Power Handling - The FQP4N90C offers higher \( I_d \) (4 A) and \( P_d \) (140 W) compared to the STP3NK90Z (3 A, 90 W), indicating it can handle higher continuous current or power under the same thermal conditions. This makes it suitable for more demanding load scenarios. 2. On‑Resistance and Test Conditions - The \( R_{ds(on)} \) of the FQP4N90C (4.2 Ω at 2 A) is slightly lower than that of the STP3NK90Z (4.8 Ω at 1.5 A), and it is specified at a higher test current. This suggests potentially lower conduction loss at higher currents, though the difference is marginal and real‑world efficiency gains will be limited. 3. Input Capacitance and Switching Behavior - The FQP4N90C has a significantly higher \( C_{iss} \) (960 pF) versus the STP3NK90Z (590 pF), reflecting greater gate charge storage. This may increase switching delay and drive losses, necessitating a redesigned gate drive circuit in high‑frequency applications (e.g., >100 kHz). 4. Threshold Voltage and Drive Compatibility - The \( V_{gs(th)} \) of the FQP4N90C (5 V at 250 µA) is higher than that of the STP3NK90Z (4.5 V at 50 µA), and the test conditions differ. This implies a slightly softer turn‑on characteristic. In low‑voltage drive environments (<8 V) or noise‑sensitive circuits, verification of full turn‑on is recommended.