Patent ID: 8030987

Claim:
A level shifter circuit comprising: a pull-up unit configured to pull up an output node to a second voltage level higher than a first voltage level in response to an input signal swinging with an amplitude of the first voltage level; a pull-down unit configured to pull down the output node in response to the input signal; and a protection unit coupled between the output node and the pull-down unit to prevent a voltage of the output node from being applied to the pull-down unit, wherein the pull-down unit comprises a first NMOS transistor having a gate receiving the input signal and a source coupled to a base voltage terminal, wherein the protection unit comprises a second NMOS transistor having a source coupled to a drain of the first NMOS transistor, a drain coupled to the output node, and a gate supplied with the input signal, wherein the first NMOS transistor is implemented with a slim transistor having a gate insulation film thickness smaller than the second NMOS transistor, wherein the base voltage terminal is a ground voltage terminal, the first voltage level corresponds to a power supply voltage, and the second voltage level corresponds to a higher-level voltage.