Comparison of Self-Biased Differential Input Stages for OTAs in 0.6-µm Flexible-Substrate Technology

In this works three differential input stages designed for operational transconductance amplifiers (OTAs) adopting IGZO plastic process are presented and compared. The differential input pairs in all the topologies are self-biased (i.e., not directly connected to bias current mirror), allowing seamless connection to a subsequent amplification stage. Based only on n-type thin-film transistors (TFT) and high-resistivity resistors, the proposed input stages preserve the common-mode bias voltage and, thus, the OTA DC operating point, even under process variations. The three input stages are simulated and characterized by embedding them within a simple, though effective, two-stage OTA structure. Performance parameters are extracted also against corner simulations revealing the robustness of all the proposed solutions.