1. TS514IDT Substitution Conclusion Direct substitution is not recommended. Although the package is compatible and the supply voltage ranges overlap, the two devices differ fundamentally in core architecture (standard BJT input vs. JFET input), resulting in significant differences in key parameters. The input bias current of the TS514IDT (50 nA) is three orders of magnitude higher than that of the TL084BCD (30 pA). This would introduce substantially larger input current errors in high-impedance signal source applications, completely negating the core advantage of high input impedance inherent to JFET op-amps. Furthermore, its slew rate (1.5 V/µs) is far lower than that of the TL084BCD (13 V/µs), severely limiting dynamic response when processing fast-changing signals (e.g., pulses, audio) and making distortion highly likely. The TS514IDT is only suitable for DC or low-frequency general-purpose amplification where input impedance and speed are not critical, and it cannot fulfill the intended JFET performance in designs originally using the TL084BCD.