1. Voltage and Saturation Voltage: The FCX1053ATA offers a higher Vceo (75V) and a significantly lower saturation voltage (Vce(sat))—440mV versus 500mV, even under a higher test current. This makes the FCX1053ATA safer in high-voltage applications and results in lower conduction loss and reduced temperature rise at the same current, which is critical for designs with stringent efficiency or thermal requirements. 2. DC Gain and Test Conditions: The FCX1053ATA has a higher minimum hFE (300 vs. 180) under a higher test current (500mA vs. 100mA). This indicates stronger and more consistent current drive capability under high load. If substituted, the bias circuit or drive current may need re-evaluation to ensure sufficient gain margin. 3. Frequency Characteristics and Leakage Current: The 2SC5824T100R has a higher transition frequency (200MHz vs. 140MHz), offering better high-frequency switching performance. However, its collector cutoff current is two orders of magnitude larger (1µA vs. 10nA). While the former is advantageous in high-speed switching applications, the latter’s lower leakage current is preferable in high-temperature or low-power-sensitive circuits, resulting in lower static power consumption. 4. Operating Temperature Range: The FCX1053ATA specifies a full industrial temperature range (–55°C to 150°C), whereas the 2SC5824T100R only lists a maximum junction temperature (150°C). The FCX1053ATA provides clearer assurance for low-temperature startup and full-temperature-range reliability, making it more suitable for demanding applications such as automotive or industrial systems. 5. Cost and Brand: The 2SC5824T100R is approximately 17% lower in cost, offering a clear price advantage. Differences in brand and supply chain (Diodes vs. Rohm) may affect supply stability and quality focus.