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.

Automated summary

The class AB two stage op-amp presented features accurate static current control, symmetric signal paths to the output transistors, and is suitable for environments with uncertain or variable supply voltages. The implementation of a conceptual floating voltage source in the output stage allows adoption of positive and negative values indistinctively. This design requires few additional devices and power consumption compared to conventional schemes, and operates within a wide range of supply voltages.