Patent ID: 7098699

Claim:
A buffer circuit device receiving differential input signals and outputting differential output signals, comprising: a buffer circuit receiving the differential input signals and outputting the differential output signals; a common mode level generator circuit having a replica circuit depending on a next-stage circuit and outputting a specific level of a common mode voltage for the differential output signals to be output from said buffer circuit: a common mode voltage detection circuit detecting a common mode voltage of specific signals; and a bias voltage adjusting circuit adjusting a bias voltage to be supplied to said buffer circuit by comparing an output signal of said common mode level generator circuit with an output signal of said common mode voltage detection circuit, wherein said common mode voltage detection circuit detects a common mode voltage of output signals of said next-stage circuit, and wherein said common mode voltage detection circuit outputs the output signal to said bias voltage adjusting circuit by processing the detected common mode voltage and an output voltage of said common mode level generator circuit, wherein said common mode voltage detection circuit comprises: a first and a second resistor elements coupling the differential output signals; and a third resistor element connected in series to an output of said common mode level generator circuit.