Noise Analysis of Translinear Circuits : Principles, Methods, and Best Practices

With the ongoing trend towards low-voltage and low-power operation, the area of analog integrated filters is facing serious challenges. Consequently, noise analysis becomes essential in designing translinear circuits, or in general, log-domain filters. Due to the inherited companding behaviour and nonstationary nature of the translinear noise sources, an efficient nonlinear noise analysis method is necessary. This work is to present several noise analysis methods for translinear circuits. Based on the large-signal calculation, the first-order noise and signal-noise intermodulation of static and dynamic translinear circuits are calculated on the basis of existing current-mode analysis methods. Then, two important noise specifications, power spectral density and signal-to-noise ratio, are specified. For dynamic translinear circuits, two methods, either combining noise sources and moving them to output, or process them in situ and individually, are elaborated. Through these methods, we can start noise analysis at early design stage, to ensure good performance. Therefore, this work should be useful to professionals in circuit design and troubleshooting.