A Low-Dropout Regulator Integrated With E-mode IGZO and D-mode ITO/IGZO Dual Layer Thin Film Transistors With Superior Uniformity and Stability

Abstract

In this work, an oxide-semiconductor-based low dropout regulator (LDO) circuit with enhancement- (E-) and depletion-mode (D-mode) thin film transistors (TFTs) is demonstrated. The E-mode TFTs adopt IGZO as the active layer. The D-mode TFTs are achieved via the ITO/IGZO dual-layer channel with high field effect mobility of 32.7 cm2V−1s−1 and superior uniformity and stability. Its threshold voltage (Vth) generates a positive shift of only 0.22V after positive bias stress. Besides, the D-mode TFTs own a low temperature coefficient of −4.9 mV/°C for Vth, facilitating the design of voltage reference. Benefiting from the remarkable D-mode TFTs, the LDO shows excellent performance, including a line regulation of 0.2%/V, a low quiescent current of $7~\mu $ A, and a load regulation of $180~\mu $ V/ $\mu $ A. It has a high power supply rejection ratio (PSRR) of up to 45 dB and a unit gain bandwidth of over 100 kHz.