1. Voltage and Current Ratings: The AOT66916L has a higher Vdss (100V) than the TK100E08N1,S1X (80V). If the original design operates with a working voltage or voltage spikes approaching 100V, substitution risks breakdown. The TK100E08N1,S1X has a much higher nominal continuous current (100A) compared to the AOT66916L (35.5A). However, this is based on its extremely low RdsOn, and the test conditions (case/ambient temperature) differ. Actual current capability is highly dependent on thermal design. 2. On-Resistance (RdsOn) Characteristics: The maximum RdsOn values are similar (3.6mΩ vs. 3.2mΩ), but the test currents differ (20A vs. 50A). This indicates the TK100E08N1,S1X offers superior conduction performance in high-current regions, while the AOT66916L may have better conduction characteristics at low-to-medium currents. This directly impacts efficiency, especially in applications with wide load current variations. 3. Dynamic (Switching) Performance: The TK100E08N1,S1X has significantly higher gate charge (Qg, 130nC) and input capacitance (Ciss, 9000pF) than the AOT66916L (Qg 78nC, Ciss 6180pF). Driving the TK100E08N1,S1X requires higher drive current or results in longer switching times, leading to higher switching losses and more demanding drive circuit requirements. This directly affects efficiency and temperature rise in high-frequency switching applications. 4. Thermal Design and Power Definitions: The AOT66916L clearly specifies power and current ratings at both ambient (Ta) and case (Tc) temperatures, facilitating evaluation under different thermal conditions. The TK100E08N1,S1X only specifies power dissipation at Tc. Its higher nominal power dissipation (255W) is entirely dependent on ideal cooling (Tc=25°C); without robust thermal management in practice, this advantage cannot be realized. The thermal characteristics of both devices must be re-evaluated based on the actual thermal part. The AOT66916L is a general-purpose MOSFET offering a balance of voltage margin and overall performance, suitable for medium-power applications below 100V. The TK100E08N1,S1X is a device focused on ultra-low conduction loss for high-current applications, but at the cost of inferior switching performance, higher drive requirements, and a limited 80V voltage rating. Any substitution requires re-evaluation of the circuit's voltage stress, drive capability, switching frequency, and thermal conditions.