US Patent 7868658 Level shifter circuits and methods for maintaining duty cycle

A circuit comprises first and second buffers, and an output buffer. The first buffer receives an input signal and provides a first buffer output signal on a first lead. The second buffer receives the input signal and provides a second buffer output signal on a second output lead. The output buffer has a first input lead coupled to the first output lead and AC coupled to the second output lead. The AC coupling communicates timing information from the second buffer to the output buffer. The first buffer applies sufficient voltage to control the first input lead of the output buffer under DC conditions.