LIQUID CRYSTAL DISPLAY DEVICE

摘要

PROBLEM TO BE SOLVED: To reduce the power consumption by making a driving voltage supply means incorporate an output stage circuit which outputs a current only in the flowout direction from the driving voltage supply means and an output stage circuit which outputs a current only in the inflow direction. SOLUTION: An operational amplifier O'P2 in place of a conventional operational amplifier and an npn type transistor TR1 which has its base connected to the output terminal of the operational amplifier O'P2 and its emitter connected to the inverted input terminal of the operational amplifier O'P2 through a resistance are used. When the voltage of a load circuit (capacitor Cs) is lower than a driving voltage Vsh, the npn type transistor TR1 supplies a current Ish to the capacitor Cs to charge the capacitor Cs so that the voltage of the capacitor Cs approximates the Vsh. If the voltage of the capacitor Cs varies and the voltage of the capacitor Cs is higher than the driving voltage Vsh, the npn type transistor TR1 turns off. Consequently, no unnecessary current flows and the electric power is not wasted.