Patent ID: 8829969

Claim:
A level-down shifter, comprising: a first load device connected between a first voltage source and a first node; a second load device connected between the first voltage source and a second node; a first input device connected between the first node and a third node, receiving a reference voltage signal, and adjusting a first node voltage of the first node based on the reference voltage signal; a second input device connected between the second node and the third node, receiving an input signal, and adjusting a second node voltage of the second node based on the input signal; and a current source connected between a second voltage source and the third node, receiving the second node voltage of the second node, and adjusting a third node voltage of the third node and a bias current based on the second node voltage of the second node, wherein: the first load device includes a first transistor, the second load device includes a second transistor, the first input device includes a third transistor, the second input device includes a fourth transistor, gate oxide thicknesses of the third and fourth transistors are larger than gate oxide thicknesses of the first and second transistors, and a voltage difference between the input signal and the second voltage source is higher than a voltage difference between the first voltage source and the second voltage source, and wherein the first input device and the second input device are connected to the current source and are not connected to another current source.