Design Approach for Ring Amplifiers

Ring amplifiers are an advantageous new amplifier architecture, but designing them needs to be done in a time consuming process using manual transient simulations. AC based design criteria are of limit usability, because of their large signal operation. This paper presents an alternative design approach for ring amplifiers. A set of cost functions and parameters is developed and the parameters' effect on the amplifier's stability, accuracy and power consumption is explained in detail. The optimization process is derived from a simple ring-amplifier model and a stability criterion. This criterion is analyzed in the context of circuit parameters, design constraints and other ring-amplifier designs. A new battery-based self-biased ring-amplifier architecture is introduced and the first stage integrator of a switched-capacitor Delta-Sigma modulator is realized using the described ring-amplifier architecture. The proposed optimization process is successfully performed using 180 nm and 40 nm technology nodes (second node with two supply voltages) and the three designs are analyzed and compared. The optimization process is derived from a basic ring-amplifier model and can be applied to other ring-amplifier structures.