1. Product Series & Qualification Level - BC848C-AU_R1_000A1 belongs to the BC848‑AU series, marked as “Automotive” grade and certified to AEC‑Q101; BC849C_R1_00001 is a general‑purpose commercial‑grade series. - AEC‑Q101 certification indicates the former has passed reliability tests specified by the Automotive Electronics Council (e.g., temperature cycling, high‑temperature/high‑humidity, lifetime validation), making it suitable for automotive environments (operating range –40°C to 150°C and higher reliability requirements). Commercial‑grade devices are not subjected to such rigorous validation; their long‑term reliability in automotive applications may be at risk. 2. Root Cause of Price Difference - BC848C-AU_R1_000A1 is priced lower ($0.16000) than BC849C_R1_00001 ($0.25000). - Such price inversion usually stems from supply‑chain strategies or volume‑purchase variations. Typically, automotive‑grade devices carry a premium due to additional testing costs. It is necessary to verify whether the supplier’s quotation reflects a long‑term stable condition, avoiding misleading part selection based on temporary price fluctuations. Additional Notes: Both devices share identical electrical parameters (Vceo, Ic, hFE, fT, etc.) and package (SOT‑23), making them functionally interchangeable. However, for high‑reliability fields such as automotive or industrial, the AEC‑Q101‑certified variant must be selected. Conversely, in consumer electronics, the two can substitute for each other, though cost and supply stability should be evaluated.