Definition: An active filter uses active components (e.g., op-amps) along with resistors and capacitors to filter signals. It provides gain and does not require inductors.

Common Types:

• Low-Pass Filter (LPF): Passes low frequencies, attenuates high frequencies.
• High-Pass Filter (HPF): Passes high frequencies, attenuates low frequencies.
• Band-Pass Filter (BPF): Passes a specific frequency range.
• Band-Reject Filter (Notch): Attenuates a specific frequency range.

Key Advantages:

• ✔ No inductors needed
• ✔ Can provide signal amplification
• ✔ High input impedance, low output impedance
• ✔ Easy to cascade stages

Design Tip: Use op-amps like LM741 or TL081; ensure proper power supply decoupling with 0.1µF ceramic capacitors near the IC.