This paper presents an operational amplifier based on pseudo-CMOS blocks and integrated in a flexible a-IGZO TFT technology. The circuit consists of only nMOS transistors, and the pair of active loads is in a pseudo-CMOS configuration. These active loads allow various kinds of common mode feedback schemes or cross-coupled connection, typical for CMOS operational amplifiers. The proposed amplifier is fabricated on a flexible film, and characterized with 5 V supply voltage and an output load capacitance of 15 pF. The measured open-loop gain is 22.5 dB, which is the highest reported for operational amplifiers in metal-oxide TFT technology. The measured bandwidth and gain bandwidth products are 5.6 kHz, and 31 kHz, respectively with 160 μW power consumption, which is lowest among flexible operational amplifies.