What is the Difference Between Active Filter and Passive Filter?

The main difference between active and passive filters lies in their components and performance characteristics. Here are the key differences:

1. Components: Passive filters are made of passive components like resistors, capacitors, and inductors, while active filters use active components like op-amps, transistors, or vacuum tubes in addition to resistors and capacitors.
2. Power Source: Active filters require an external power supply to operate, whereas passive filters do not need an external power source.
3. Frequency Range: Passive filters are most responsive to a frequency range from approximately 100 Hz to 300 MHz. Careful design practices can extend their use well into the gigahertz range. Active filters can deal with very low frequencies (approaching 0 Hz) and can provide voltage gain, which passive filters cannot.
4. Loading Effect: The output of passive filters changes with the load, whereas active filters maintain their performance irrespective of the load connected.
5. Gain: Passive filters cannot apply additional gain to the signal, whereas active filters can adjust the gain.
6. Size and Weight: Active filters are compact and have a small size and weight, while passive filters are bulkier due to inductor size and heavier, especially at low frequencies.

Active filters are generally preferred in the field of communication and signal processing due to their ability to provide voltage gain and maintain performance irrespective of the load connected. However, passive filters are easier to construct and relatively inexpensive, making them suitable for certain applications.

Comparative Table: Active Filter vs Passive Filter

Here is a table summarizing the differences between active and passive filters:

In summary, active filters use active components like op-amps and transistors, require a power source, and offer better performance and gain compared to passive filters. Passive filters, on the other hand, use passive components like resistors, inductors, and capacitors, do not require a power source, and have simpler designs but are more sensitive to loading effects when cascaded with other filters.