Original Part
Alternative Part
1. TL084ID Substitution Conclusion
The TL084ID can serve as a downgraded replacement for the AD8684ARZ-REEL, suitable only for general-purpose applications where high precision and low power consumption are not critical. Although both are quad-channel JFET op-amps with compatible packages, the TL084ID exhibits significantly poorer performance in key parameters: its input bias current (30 pA) and input offset voltage (3 mV) are approximately 5 times and nearly 10 times worse, respectively, than those of the original part (6 pA, 350 µV). In circuits requiring low input current and high DC precision—such as high-impedance sensor amplification or precision measurement—the TL084ID will introduce considerable error. Furthermore, its supply current (1.4 mA per channel) is higher, making it unsuitable for low-power designs. However, the TL084ID offers a higher slew rate (13 V/µs), which may be advantageous for fast signal transitions.
2. LF347BD Substitution Conclusion
The LF347BD is closer to the original part in terms of output drive capability and supply voltage range, but it remains unsuitable for precision applications. Its input bias current (50 pA) and offset voltage (3 mV) are far less accurate than those of the AD8684, and its quiescent current (8 mA per channel) is about 38 times higher than that of the original part (210 µA per channel). In battery-powered or power-sensitive applications, this will lead to significant heat generation and reduced operating life. The advantage of the LF347BD lies in its stronger output current (31 mA), which allows it to drive heavier loads—such as small motors or multi-stage filters—directly, whereas the AD8684 is limited to 12 mA. Therefore, substitution should only be considered in scenarios where drive capability is prioritized and the trade-offs of higher power consumption and lower precision are acceptable.
Analysis ID: B4C7-14B7000
Based on part parameters and for reference only. Not to be used for procurement or production.
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