1. DC Current Gain (hFE): The minimum hFE of DDTC123JLP-7 is 180 at Ic = 50 mA, Vce = 5 V, which is substantially higher than the 35 at Ic = 5 mA, Vce = 5 V for PDTC123YMB,315. Under the same base current, DDTC123JLP-7 can deliver much higher collector current or require significantly lower base drive current for the same load. Direct substitution may result in overdrive or underdrive in the original circuit. 2. Internal Bias Resistor Network (R2): The pull‑down resistor R2 of DDTC123JLP-7 is 47 kΩ, compared to 10 kΩ for PDTC123YMB,315. The higher R2 gives DDTC123JLP-7 a higher input impedance (lighter load) for the same input voltage, but also provides weaker pull‑down at the base, which may slightly reduce turn‑off speed or affect noise immunity. 3. Saturation Voltage Test Conditions: Vce(sat) for DDTC123JLP-7 is specified at Ic = 50 mA, while for PDTC123YMB,315 it is specified at Ic = 10 mA. This indicates that the DDTC123JLP-7 datasheet emphasizes its saturation behavior at higher currents; in practice, its Vce(sat) at 10 mA could be well below 200 mV. However, direct comparison of this parameter requires attention to the differing test conditions. 4. Quality Qualification: PDTC123YMB,315 is explicitly marked as “Automotive” grade and is AEC‑Q100 qualified, whereas DDTC123JLP-7 does not mention such qualification in its parameters. This difference is critical for applications in harsh environments such as automotive electronics.