A Common Drain Operational Amplifier Using Positive Feedback Integrated by Metal-Oxide TFTs

Abstract

This paper presents a common-drain-based operational amplifier (OPAMP) fabricated by mono n-type indium-zinc-oxide (IZO) thin-film transistors (TFTs). Positive feedback technology is employed to the load TFTs by cross-coupled connection in order to boost the voltage gain of the common-drain differential pair. The OPAMP exhibits an open-loop voltage gain (Av) of 27 dB over a -3 dB bandwidth (BW) of 8.4 kHz at a DC supply voltage of 10 V. The measured unity-gain frequency (UGF), phase margin (PM) and DC power consumption are 119.4 kHz, 36° and 0.96 mW, respectively. Moreover, the chip area of the proposed OPAMP is as small as 0.37 mm ×0.3 mm since this concise topology needs only 10 TFTs.