Two-Stage CMOS Op-Amp (2): High-Frequency Response

Two-Stage CMOS Op-Amp (2): High-Frequency Response

by Vincent Chang

Formal & Physical Sciences Engineering & Technology TJFElectronics engineeringTJFCElectronics: circuits and components
🎙 Vincent Chang 👥 2K 📅 November 14, 2021 ⏱ 19 min 👁 703 📄 tutorial 🧭 2026-08-17
Available in: English (current) Français

Keywords

CMOS op-amphigh-frequency responseMiller compensationdominant poleunity-gain frequency

Summary

This lecture, part of a series on two-stage CMOS op-amps, focuses on the high-frequency response. The instructor begins by reviewing the low-frequency equivalent circuit and then introduces the high-frequency model, which includes the Miller compensation capacitor (Cc) and internal capacitances (C1 and C2). He poses the question of where the dominant pole is located and proceeds to derive the high-frequency transfer function. Using the dominant pole assumption, he shows that the dominant pole frequency is approximately 1/(R1Ccgm2R2), where gm2R2 is the gain of the second stage. He then derives the unity-gain frequency, which simplifies to gm1/Cc, and introduces an ‘integrator model’ as a shortcut: by assuming the second stage gain is infinite, the circuit reduces to a Miller integrator, yielding the same unity-gain frequency. The lecture emphasizes the importance of hand analysis for intuition and suggests using simulation for precise results. The next lecture will cover offset voltage cancellation.

149 words

Critical Evaluation

Value of the Information & Strength of the Argument

The lecture provides valuable insights into the high-frequency behavior of two-stage CMOS op-amps, a fundamental topic in analog IC design. The instructor’s step-by-step derivation of the dominant pole and unity-gain frequency is clear and pedagogically effective. He uses the Miller effect to simplify the analysis and introduces an intuitive integrator model that captures the essence of the high-frequency response. The argumentation is solid, based on standard approximations and self-consistent assumptions. The emphasis on hand analysis for intuition is valuable for students and engineers.

Scientific Rigor, Source Quality, Title Accuracy

The scientific rigor is adequate for a tutorial: the derivations follow conventional textbook methods, and the instructor’s expertise is evident. However, no external sources are cited, and the content is not peer-reviewed. The title accurately reflects the content, and the lecture is well-structured. The video does not include any sponsored content.

149 words

Title / Content Match

The title accurately reflects the content, which focuses on the high-frequency response of a two-stage CMOS op-amp.

Quality & Reliability

7/10

The content is based on established analog IC design principles, presented by an experienced educator. The reasoning is clear and follows standard textbook approaches, but no external sources are cited, and the video is a tutorial rather than a peer-reviewed presentation.

Key Moments

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

Contribution & Novelties

The lecture provides a clear pedagogical approach to understanding the high-frequency response of two-stage CMOS op-amps, emphasizing the integrator model as an intuitive shortcut. This model simplifies the analysis and helps engineers quickly estimate the unity-gain frequency. The lecture also reinforces the importance of hand analysis for developing intuition, complementing simulation-based design.

Pour aller plus loin :

  • Miller effect — The Miller effect is central to the compensation technique discussed.
  • Operational amplifier compensation — Provides broader context on frequency compensation techniques.
  • Pole splitting — Related to the dominant pole approximation and Miller compensation.

93 words

Radar Profile

The radar profile shows high scores in quality and technical level, with moderate scores in quantity and reliability. This indicates a technically deep tutorial with solid content, but limited breadth and lack of external references.

Reliability 7/10