What is the difference between active and passive filters in instrumentation?

Passive filters use only resistors, capacitors, and inductors - no amplification, limited frequency response shaping, simple and reliable, but signal loss and loading effects. Active filters use op-amps with RC networks - provide gain, sharper cutoff characteristics, no inductors (smaller, cheaper), flexible design, but require power and limited by op-amp bandwidth. Active filters are preferred for precision instrumentation due to better performance. Common topologies: Butterworth (flat passband), Chebyshev (sharp cutoff), and Bessel (linear phase, good for pulse preservation).