Design of Robust CMOS Amplifiers Combining Advanced Low-Voltage and Feedback Techniques

This paper describes and tries to demystify the use of different lowvoltage operation devices, such as dynamic threshold MOS transistors (DTMOS) with feedback techniques such as regulated-feedforward (RFF) and self-biasing (SB). Traditionally, DTMOS devices are only used when nominal supply voltages below 0.7 V are envisaged. Moreover, RFF and SB techniques are normally avoided since engineers designing high-performance amplifiers are afraid of additional stability concerns. This work demonstrates, through exhaustive simulation results over process, temperature and supply (PVT) corners using a standard 130 nm 1.2 V CMOS technology that, employing DTMOS in some specific devices can improve some performance parameters such as the open-loop low-frequency gain and, simultaneously, reduce significantly the variability over PVT corners. Moreover, it is also demonstrated that, there is no risk of operating at supply voltages higher than 1.2 V. Combining DTMOS with RFF and SB allows achieving reasonable gainbandwidth products (GBW) even operating at low-voltage (down to 0.7 V), together averaged power savings of the order of 8% and highly simplifies the design of the circuit (since no biasing circuitry is required).