Abstract: The fundamental principle of quasi-floating gate transistors, along with the electrical characteristics and equivalent circuits, are discussed. An ultra-low voltage operational amplifier is proposed using the PMOS quasi-floating gate transistors. Based on the TSMC 0.25μm CMOS process, the whole circuit is simulated by using the Hspice simulator. The simulation result shows that, with a single power supply of 0.8V, the maximal open-loop gain of the amplifier is 76.5dB, the phase margin is 62°, the unit gain band width is 2.98MHz and the power dissipation is only 9.45μW.

Key words: quasi-floating gate, ultra-low voltage, operational amplifier, CMOS