Enhancing the bandwidth of a-IGZO TFT amplifiers using circuit design techniques

Abstract

Amorphous oxide thin-film transistor (TFT) technology has become central in flexible and low-cost electronic applications. However, there are some limitations of the technology for circuit implementation, particularly the lack of stable and reproducible p-type oxide TFTs, limited speed due to poor semiconductor mobility and to large channel lengths when com-pared to single crystalline Si devices. These limitations demand novel circuit design techniques using only n-type TFTs to achieve high-speed circuits meeting the requirement of practical applications. This work aims to improve the low unity current gain frequency of operation of a-IGZO based amplifiers using only circuit-based techniques, without changing the device structure, fabrication steps and materials. Simulations in Cadence environment were performed in five different amplifier structures, employing a-IGZO TFTs based on an in-house model developed with artificial neural networks. Up to three-fold improvement on bandwidth was verified, with minimal increases in power consumption and chip area. The concepts explored here are thus quite relevant to enhance low-MHz range circuits, as required for RFID and biomedical applications.