Patent ID: 7138996

Claim:
A common voltage regulating circuit of a liquid crystal display device, comprising: a pulse signal generating means for outputting a pulse width modulation signal in response to up/down signal for adjusting a common voltage; a first resistor receiving the pulse width modulation signal through a first end and a first capacitor coupled between the resistor's second end and a ground, said first resistor and first capacitor smoothing the pulse width modulation signal to produce a smoothed pulse width modulation signal; and an amplifier having a non-inverting input terminal coupled to the resistor's second end, amplifying the signal smoothed by the first resistor and first capacitor to a predetermined level and outputting a common voltage signal, wherein said amplifier includes a second resistor coupled between an inverting terminal of said amplifier and an output terminal, a third resistor coupled between the inverting terminal of said amplifier and a ground, and said amplifier amplifies the smoothed pulse width modulation signal to a predetermined level in order to output the common voltage signal.