1. Current Capability & On-Resistance: The TK6A45DA features a significantly higher continuous drain current (5.5A @ Ta) compared to the IRFI830GPBF (3.1A @ Tc). Furthermore, its on-resistance remains superior even at a higher test current (1.35Ω @ 2.8A vs. 1.5Ω @ 1.9A). This gives the TK6A45DA greater power handling capability and lower conduction losses. 2. Dynamic (Switching) Performance: The TK6A45DA's total gate charge (Qg=11nC) is substantially lower than that of the IRFI830GPBF (Qg=38nC). Combined with its lower input capacitance, this results in faster switching speeds, significantly lower switching losses, and simpler drive circuit requirements. 3. Thermal Performance & Rating Conditions: The TK6A45DA's current is rated at ambient temperature (Ta), whereas the IRFI830GPBF's is rated at case temperature (Tc). The latter is a more stringent industrial standard. Despite this, its absolute current rating remains much lower, which directly restricts its application at the original design's power level. 4. Package & Isolation: The IRFI830GPBF uses an isolated-tab surface-mount package, which can eliminate the need for an insulating washer but may compromise thermal performance. The TK6A45DA's TO-220SIS package requires insulation consideration. This impacts mechanical mounting and thermal design but does not change the core electrical barrier to substitution.