Understanding Analog Filters: Types, Designs, and Frequency Response Characteristics

Introduction

Electronic filters are used everywhere inside the electronic system. Its primary purpose is signal conditioning. Signal conditioning is based on performance requirements. In this article, we will go over basic four types of filter and filter examples.

Background

Filter Type

  |--- R ---|--- 

  |              |

  |            --- C

  |            ---

  |              |

  |---------|---


  |--- L ---|--- 

  |              |

  |             R

  |              

  |---------|---


  |--- R + L ---|--- 

  |                     |

  |                   --- C

  |                   ---

  |                     |

  |-------------|---


  |--- C ---|--- 

  |              |

  |             R

  |         

  |---------|---


  |--- R ---|--- 

  |              |

  |              L

  |         

  |---------|---


  |--- R + C ---|--- 

  |                     |

  |                    L

  |         

  |-------------|---


  |--- L + C ---|--- 

  |                     |

  |                    R

  |         

  |-------------|---



  |--- R ---|--- 

  |              |

  |          L || C

  |         

  |---------|---



  |--- R ---|--- 

  |               |

  |           L + C

  |         

  |---------|---


  |--- L || C ---|--- 

  |                     |

  |                    R

  |         

  |-------------|---


Filter Characteristics

Below is depiction for for filter characteristics:

Here's how the key characteristics of a filter are represented in these plots:

Analog Filter

Digital Filter

Design Analysis

Digital Circuit

Power Circuit

RF Desense Circuit

Audio Processing

Q&A

What is the most commonly used filter for electronic system design for digital designers?

Low Pass filter!

Summary & Conclusion

Filter is widely used to conditioning signal transmissio within the electronic system. Understanding basic filter type and different real world filter components and application enables electronic system engineers to break down any filter design into its basics four types. We omitted more complex filter design used in RF world such as Chebychev, Butterworth, Ellipication,etc but provided link for anyone to play around with.

Further Reading/Practice

"Analog Filters", https://www.analog.com/media/en/training-seminars/design-handbooks/Basic-Linear-Design/Chapter8.pdf 

"Filter Design and Tool", http://sim.okawa-denshi.jp/en/Fkeisan.htm 

"RF LC RF Design Tool", https://rf-tools.com/lc-filter/