Question

The problem of passive filters is overcome by using

(a) Analog filter

(b) Active filter

(c) LC filter

(d) A combination of analog and digital filters

The question was asked in semester exam.

Query is from Active Filters in division Active Filters of Linear Integrated Circuits

Answer 1

The correct answer to this question is:

(b) Active filter

Explanation:

• Active filters use active components like operational amplifiers (op-amps), along with passive components (resistors and capacitors), to achieve filtering. These filters overcome the limitations of passive filters, which can only use resistors, capacitors, and inductors.

Advantages of Active Filters:

• No need for inductors: Inductors can be bulky, expensive, and difficult to implement in some circuits. Active filters replace inductors with operational amplifiers, making the design more compact and cost-effective.
• Better performance: Active filters can provide gain and have more flexible frequency responses. They can also achieve higher-order filtering with fewer components.
• Improved stability and precision: Active filters typically have better performance in terms of frequency stability and precision than passive filters.

Why not the other options?

• Analog filter: This term refers to filters that use continuous-time analog circuits, which can include both passive and active filters. However, it does not specifically address the problem of passive filters (e.g., the use of inductors and limited gain).
• LC filter: An LC filter is a type of passive filter that uses inductors and capacitors. While it’s useful in some applications, it does not overcome the problems associated with passive filters, like the need for inductors and limited gain.
• A combination of analog and digital filters: While combining analog and digital filters is common in certain applications, it’s not a direct solution to the limitations of passive filters, especially regarding gain and the use of inductors.

Thus, active filters are the correct answer because they overcome the limitations of passive filters, such as the need for inductors and limited gain.