1. Vce(sat) and hFE: The 2SCR513PT100 exhibits a significantly lower saturation voltage (350mV) compared to the BCX54,115 (500mV). Furthermore, its minimum DC current gain (hFE_min=180) is substantially higher than that of the BCX54,115 (hFE_min=63). Under identical load current conditions, the replacement device offers lower switching losses and higher efficiency. It also requires less base current to drive the same collector current, thereby reducing the burden on the preceding driver stage. 2. Transition Frequency (ft): The ft of the 2SCR513PT100 (360MHz) is twice that of the BCX54,115 (180MHz), indicating superior high-frequency performance. This makes it suitable for amplification or switching circuits operating at higher frequencies. However, careful attention must be paid to PCB layout, as the device may be more susceptible to parasitic effects in high-frequency designs. 3. Power Dissipation: The maximum power dissipation of the 2SCR513PT100 (2W) is 60% higher than that of the BCX54,115 (1.25W). For a given thermal design, this provides greater power headroom, lower junction temperature rise, and consequently improved reliability. 4. ICBO: The collector cutoff current of the 2SCR513PT100 (1µA) is one order of magnitude higher than that of the BCX54,115 (100nA). In applications involving high temperature or high reverse voltage, this may result in slightly higher leakage current, which could be a concern for low-power or high-precision analog circuits. 5. Cost: The unit price of the 2SCR513PT100 ($0.85) is approximately 77% higher than that of the BCX54,115 ($0.48). This cost premium must be carefully weighed in cost-sensitive designs.