1. Working principle
Passive filters mainly rely on passive components such as capacitors, inductors, resistors, etc. to filter signals. They can only process the low-frequency, mid frequency, and high-frequency parts of the input signal and filter them out separately. Passive filters do not have amplifiers, so they cannot increase the strength of the signal. Common passive filters include RC filters, RL filters, LC filters, etc.
Active filters can enhance signal strength and filter specific frequencies in the signal. They use amplifiers to amplify input signals and then feed them into filter circuits to provide the required signal processing. Common active filters include low-pass filters, high pass filters, band-pass filters, and band stop filters.
2. Bandwidth


3. External power supply


4. Stability