Active Filters
Electronic circuits that use operational amplifiers and passive components to selectively process frequency components of signals, providing amplification and enhanced performance compared to passive filters.
Active Filters
Basic Principles
Active filters combine operational amplifiers with passive components (resistors, capacitors, and sometimes inductors) to achieve:
- Signal filtering with amplification
- Higher input impedance and lower output impedance
- Better frequency response control
- Elimination of bulky inductors in many designs
Core Classifications
By Response Type
- low-pass filter - Passes frequencies below cutoff
- high-pass filter - Passes frequencies above cutoff
- band-pass filter - Passes a specific frequency range
- notch filter - Rejects a specific frequency range
- all-pass filter - Modifies phase while maintaining amplitude
By Circuit Topology
Design Characteristics
Key Parameters
Filter Responses
- Butterworth response - Maximally flat magnitude
- Chebyshev response - Steeper rolloff with ripple
- Bessel response - Optimal phase response
- Elliptic response - Sharpest cutoff with ripple
Implementation Considerations
Component Selection
- precision resistors
- stable capacitors
- op-amp bandwidth requirements
- component matching considerations
Performance Optimization
Applications
Audio Processing
Instrumentation
Communications
Advanced Topics
High-Order Filters
Modern Developments
- switched capacitor filters
- digital-analog hybrid filters
- adaptive filtering
- integrated filter design