Black-Box Modeling Approach with PGB Metric for PSRR Prediction in Op-Amps

The rapid development of electronic technology has generated the demand for low - power and high- performance circuit design. The key indicator, power supply rejection ratio (PSRR), is crucial for circuit design. Given the deficiencies of existing PSRR calculation methods in high-frequency applications and complex circuit designs, this pa-per proposes an innovative PSRR calculation theory. Based on a simplified circuit model, this theory uses Thevenin's equivalent principle to transform multi-stage operational amplifiers into a black-box model, simplifying the calculation process and enhancing the intuitiveness of calculation. In view of the characteristics of industrial design, we also proposed the PSR Gain Bandwidth (PGB) theory, which can more intuitively analyze the trade-off between PSRR and other performance within the target range. This paper further explores the impact of different circuit structures on PSRR characteristics, covering typical circuit structures such as PMOS/NMOS input two-stage operational amplifiers and folded cascode operational amplifiers, and deeply analyzes the key factors affecting PSRR characteristics. The effectiveness of the proposed theory is verified through case analysis, and its potential applications in circuit designs with high PSRR requirements are demonstrated.