An a-IGZO TFT based Op-Amp with 57 dB DC-Gain, 311 KHz Unity-gain Freq., 75 deg. Phase Margin and 2.43 mW Power on Flexible Substrate

Abstract

This paper presents an internally compensated two stage operational amplifier fabricated using unipolar a-IGZO TFT devices integrated on flexible polyimide substrate. A new active load configuration is introduced to realize high incremental impedance and serve as the stage load of the amplifier. The opamp has been manufactured and measured to have 57 dB of open-loop DC-gain and a unity gain frequency of 311 kHz. Further, the internal compensation sets the dominant pole of the opamp achieving a phase margin of 75 degrees. A common mode feedback scheme has been implemented to bias the fully differential gain stages using an auxiliary two-stage OpAmp realized with a conventional diode-connected transistor stage load. This design, to our knowledge, surpasses the highest reported performance of (operational) amplifiers made in a-IGZO technology.