A 70°phase margin OPAMP with positive feedback in flexible a-IGZO TFT technology

This paper presents a fully integrated operational amplifier (OPAMP) with positive feedback fabricated in a flexible amorphous indium gallium zinc oxide (a-IGZO) thin film transistor (TFT) technology. The OPAMP is implemented by using a 5 μm nMOS a-IGZO TFT process, and is operated from a dc supply voltage of 6 V. The circuit relies on positive feedback in the input differential pair to improve gain. The measured open-loop gain is 19 dB over a 3 dB bandwidth of 25 kHz with 70° PM (phase margin). The measured unity-gain frequency, output swing voltage, and dc power consumption are 330 kHz, 3.7 V_pp, and 6.78 mW, respectively. The total chip area of the proposed OPAMP is 4.2×6 mm². To the best of our knowledge the proposed amplifier has the highest PM among OPAMPs in TFT technology.