A 6-bit Analog-to-Digital Converter for Electromyography Implemented Using N-Type Metal-Oxide Thin-Film Transistors

Consisting of more than 2000 n-type metal-oxide thin-film transistors (TFTs), a 6-bit analog-to-digital converter (ADC) adopting the subranging architecture is designed, fabricated, characterized and applied to digitize an electromyogram (EMG). Consisting of amplifiers each with a feedback stage for gain-boosting, the comparators at the heart of the ADC incorporate a scheme for compensating the offset error arising from the inevitable non-uniformity of the TFT parameters. Compared to the specifications of reported ADCs based on TFTs, a higher sampling rate of 1000 S/s, a smaller differential non-linearity of 0.76 least-significant bit (LSB) and a smaller integral non-linearity of 0.88 LSB are achieved. Since the same low-temperature TFT technology for fabricating the EMG acquisition system on a flexible substrate is used to construct the ADC, the two could be readily monolithically integrated.