Comparator With Non-Uniform Parameter Compensation Using Dual-Gate Thin-Film Transistors

Benefitting from the availability of a top gate serving as an “auxiliary” input terminal, a dual-gate (DG) thin-film transistor (TFT) can be incorporated in a circuit and used to mitigate potential performance degradation induced by the inevitable variation in TFT parameters. The utility of this scheme is demonstrated with the design, fabrication and characterization of a comparator. Compared to the traditional output storage compensation scheme deployed in state-of-the-art comparators based on conventional single-gate TFTs, the present scheme based on DG TFTs offers a reduction in amplifier stage count to 2 from 4 or 5, a reduced TFT count of 9, and a reduction in offset error from ~0.4 V to 14 mV for comparators with D flip-flop while operating at a sampling rate of 2000 samples/s. The TFTs are fabricated using a 300-°C metal-oxide TFT technology, potentially enabling their monolithic integration with bio-potential sensing circuits on a flexible substrate.