Patent ID: 7705630

Claim:
A negative voltage level shifter, comprising: a first inverter comprising an input end for receiving an input signal and an output end for outputting a first internal signal, the first inverter being powered with a positive supply voltage and performing an inverting operation on the input signal for generating the first internal signal; a pass unit comprising an input end electrically connected to the output end of the first inverter for receiving the first internal signal and an output end for outputting a second internal signal, the pass unit enabling an electrical connection between the input and output ends thereof when the first internal signal has a voltage greater than a threshold voltage, the pass unit disabling the electrical connection between the input and output ends thereof when the first internal signal has a voltage less than the threshold voltage; a voltage-dividing unit comprising a first end electrically connected to the output end of the pass unit for receiving the second internal signal, a second end for receiving a negative supply voltage, and a third end for outputting a third internal signal having a voltage divided from the negative supply voltage and the second internal signal based on a circuit operation of superposition theory; a second inverter comprising an input end electrically connected to the third end of the voltage-dividing unit for receiving the third internal voltage and an output end for outputting a fourth internal signal, the second inverter being powered with the negative supply voltage and performing an inverting operation on the third internal signal for generating the fourth internal signal; and a third inverter comprising an input end electrically connected to the output end of the second inverter for receiving the fourth internal voltage and an output end for outputting an output signal, the third inverter being powered with the negative supply voltage and performing an inverting operation on the fourth internal signal for generating the output signal.