Active Filter Based on Inductor Replacement (3): All-Pass

Active Filter Based on Inductor Replacement (3): All-Pass

by Vincent Chang

Formal & Physical Sciences Engineering & Technology TJFElectronics engineeringTJFCElectronics: circuits and components
🎙 Vincent Chang 👥 2K 📅 November 7, 2021 ⏱ 12 min 👁 284 📄 tutorial 🧭 2026-08-17
Available in: English (current) Français

Keywords

all-pass filtercomplementary transformationband-pass filteractive filtercircuit design

Summary

This video is part of a series on active filters based on inductor replacement, focusing on the all-pass filter. The instructor, Vincent Chang, begins by reviewing the relationship between all-pass and band-pass filters, showing that the sum of the all-pass transfer function and twice the band-pass transfer function equals one. He introduces the concept of complementary transformation, using the inverting and non-inverting amplifiers as a simple example. The main exercise is to derive the all-pass circuit from a band-pass circuit with a center frequency gain of two by swapping the input and ground connections. The instructor demonstrates the transformation step-by-step, then shows how to derive the transfer function of the resulting all-pass filter without resorting to ‘mathematical violence’, by leveraging the known band-pass transfer function. The key takeaway is the skill of complementary transformation, which simplifies circuit design. The video concludes with a preview of the next topic: the two-integrator loop.

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Critical Evaluation

Value of the Information & Strength of the Argument

The video provides valuable insights into the design of all-pass filters using complementary transformation, a technique that simplifies circuit derivation. The argumentation is logical and builds on previous knowledge, making it accessible for those familiar with basic filter theory. The instructor emphasizes a ‘smart’ approach over brute-force calculation, which is pedagogically effective. However, the video lacks formal proofs or references, relying on the instructor’s authority.

Scientific Rigor, Source Quality, Title Accuracy

The scientific rigor is moderate: the content is technically sound but lacks citations to external sources. The instructor’s credentials lend credibility, but the absence of references reduces the verifiability. The title accurately describes the content, and the video is well-structured. No comments were provided for analysis.

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Title / Content Match

The title accurately reflects the content, which focuses on the all-pass filter as part of a series on active filters based on inductor replacement.

Quality & Reliability

7/10

The content is presented by an experienced educator with 30 years in the field, but the video lacks formal citations and references. The explanations are clear and logically structured, but the absence of sources and the reliance on the instructor's authority reduce the overall reliability score.

Key Moments

Markers derived by PSI from the transcript: the creator did not define chapters.

Contribution & Novelties

The video’s original contribution lies in its pedagogical approach to teaching all-pass filter design through complementary transformation, a technique that simplifies circuit derivation. It provides a clear, step-by-step method that can be applied to other filter types.

Pour aller plus loin :

  • All-pass filter — Wikipedia article providing background on all-pass filters.
  • Band-pass filter — Wikipedia article on band-pass filters, relevant to the discussed relationship.
  • Operational amplifier — Wikipedia article on op-amps, essential for understanding the circuits.

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Radar Profile

The radar profile shows a balanced performance with high scores in technical level and information quality, indicating a technically rich and informative video. The lower score in information quantity suggests that the video is concise and focused, while the reliability score is moderate due to lack of citations.

Reliability 7/10