1. ICL7621DCBAZ Substitution Conclusion Direct substitution is not recommended. While both devices share identical basic parameters such as supply voltage range and input bias current, there are significant differences in key performance specifications. First, the slew rate (0.16 V/µs) and gain bandwidth product (480 kHz) of the ICL7621DCBAZ are substantially lower than those of the original part (1.6 V/µs, 1.4 MHz). This results in a considerable reduction in signal processing speed and large-signal frequency response capability, rendering it unsuitable for moderate-speed or moderate-frequency analog signal applications that the original device can handle. Second, the original part is explicitly specified as having "rail-to-rail output," whereas the ICL7621DCBAZ does not list this feature. It is highly likely that its output voltage cannot swing close to the supply rails. This severely limits the output dynamic range under low-voltage supply conditions, potentially leading to signal clipping or degraded accuracy. Finally, while the ICL7621DCBAZ has a lower quiescent current (100 µA per channel), its output current capability (1 mA) is potentially limited, which may constrain its ability to drive low-impedance loads. Substitution could only be cautiously considered in applications with extremely low requirements for speed and output swing. Otherwise, it is not a viable alternative.