Op amp subtractors, integrators, differentiators, and inverters have various practical applications in electronics. Subtractors can function as comparators, which are useful for signal processing. Integrators are often used as low-pass filters, while differentiators serve as high-pass filters, enhancing signal processing capabilities. Active filters, which incorporate op amps, offer advantages over passive filters due to their amplification properties. Understanding these applications is essential for measuring phase differences in signals, such as using an integrator to derive DC voltage proportional to the phase difference between square waves.