Digital OTAs: Conventional Designs Versus Emerging Concept

This brief presents two novel fully digital operational transconductance amplifier (OTA) architectures for low-voltage CMOS technologies. The first design is a fully differential OTA that replaces conventional inverter-based gain stages with Müller C-elements, exploiting their regenerative and state-retentive properties to enhance effective voltage gain without DC biasing or analog support circuitry. The second introduces an emerging concept in which a latch-based comparator is reinterpreted as a continuous-time OTA through controlled charge transfer to an output capacitor using predominantly standard digital cells. Both approaches eliminate traditional analog biasing while preserving rail-to-rail operation and zero static power in steady state. A comparative analysis highlights their operating principles and scalability for digitally intensive mixed-signal systems.