A Solution-Processed Operational Amplifier Using Direct Light-Patterned a-InGaZnO TFTs

In this paper, we present a novel operational amplifier (op-amp) composed with solution-processed n-type amorphous indium-gallium-zinc-oxide (a-InGaZnO) thin-film transistors (TFTs). For patterning a-InGaZnO layer, we used direct light patterning method that drastically reduces the process steps and costs compared to conventional vacuum processes. The a-InGaZnO TFT-based op-amp was designed and fabricated on a glass substrate yielding a total gain of 24.6 dB, a cutoff frequency of 0.47 kHz, and a unit-gain frequency of 2.0 kHz at a supply voltage of ±15 V. Finally, by constituting a pulsewidth modulation controller with the proposed op-amp, we confirmed that the duty ratio and output voltage of the comparator and error amplifier could be altered with respect to the reference voltage, respectively.