access icon free High gain operational amplifier and a comparator with a-IGZO TFTs

© The Institution of Engineering and Technology
Received 10/06/2020, Accepted 20/07/2020, Revised 14/07/2020, Published 17/08/2020

This study presents a novel high gain operational amplifier (op-amp) and a comparator using n-type all enhancement amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The proposed op-amp employs regulated cascode topology in conjunction with capacitive bootstrap load, which enhances the gain to 159.87% (V/V) as compared to op-amp with bootstrapping load. In addition, common mode feedback is introduced in the circuit which improves the common-mode rejection ratio (CMRR) of the amplifier without hampering the output voltage swing. The proposed op-amp offers a voltage gain of 46.2 dB, phase margin of 67°, CMRR of 51.8 dB, unity gain frequency of 215 kHz and power consumption of 0.22 mW. Furthermore, a novel comparator circuit at a clock frequency of 50 kHz is reported. The power consumption of the circuit is 0.248 mW and it can discriminate a minimum voltage of 50 mV. The performance of the proposed circuits is demonstrated using an analytical model of a-IGZO in Cadence environment with a channel length of 20 µm at a supply voltage of 10 V. Further with the help of the circuits reported in this work, many sensing systems of practical importance can be developed, such as smart packaging and bio-medical wearable devices using flexible electronics.

Inspec keywords: low-power electronics; semiconductor device models; comparators (circuits); bootstrap circuits; operational amplifiers; indium compounds; amorphous semiconductors; thin film transistors

Other keywords: common-mode rejection ratio; voltage 10.0 V; gain 46.2 dB; sensing systems; regulated cascode topology; capacitive bootstrap load; op-amp; a-IGZO TFT; voltage 50.0 mV; power 0.248 mW; bootstrapping load; InGaZnO; voltage gain; frequency 50.0 kHz; common mode feedback; power consumption; frequency 215.0 kHz; output voltage swing; power 0.22 mW; size 20.0 mum; amorphous indium-gallium-zinc-oxide thin-film transistors; unity gain frequency; n-type all enhancement thin-film transistors; Cadence environment; comparator circuit; high gain operational amplifier; CMRR

Subjects: Electrical/electronic equipment (energy utilisation); Amplifiers; Other analogue circuits; Other field effect devices; Semiconductor device modelling, equivalent circuits, design and testing

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