Class AB Op-Amp With Accurate Static Current Control for Low and High Supply Voltages

A class AB two stage op-amp with accurate static current control, symmetric signal paths to the output transistors, and suitable for environments with uncertain or variable supply voltages is presented. The implementation of the conceptual floating voltage source for the push pull operation in the output stage has the ability to adopt positive and negative values indistinctively by means of a resistor with bidirectional currents driven by a control circuit. The latter requires very few additional devices and power consumption compared to the conventional scheme and is capable of operating with supply voltages as low as a gate-source voltage and a saturation voltage of a transistor, and as high as permitted by design and technology. Experimental results from a fabricated prototype in 0.5 mu m technology show the class AB operation of the amplifier driving a load capacitance of 16 pF.