A circuit includes an output node, a set of first transistors, a set of second transistors, and a first and second power node. The first power node is configured to carry a first voltage level, and second power node is configured to carry a second voltage level. Set of first transistors is coupled between the first power node and output node. Set of second transistors is coupled between the second power node and output node. The first control signal generating circuit is coupled to a gate of a first transistor of the set of first transistors and a gate of a first transistor of the set of second transistors. The first control signal generating circuit is configured to generate a set of biasing signals for the gate of the first transistor of the set of first transistors and the gate of the first transistor of the set of second transistors.