| 摘要 |
<p>PURPOSE:To vary and control a supply voltage level according to variation in resistance value with the temperature of a thermistor by providing a voltage control element which controls the supply voltage level of a voltage supply terminal according to the output level of an operational amplifier. CONSTITUTION:When the operation temperature of TFD-LCD rises, the resistance value of the thermistor R3 falls and at this time, a PNP type transistor TR is so controlled that an inverted input side voltage corresponding to the level at the voltage division point between voltage dividing resistances R2 and R1 is always equal to the uninverted input side voltage of a ground line GND. Consequently, the supply voltage level '-Vout' controlled by the transistor TR rises along an optimum driving voltage V0 and its voltage adjustment range A also slides according to the supply voltage level '-Vout'. Therefore, the voltage variation range A of a variable resistance element VR1 may be extremely small and the best contrast on a display screen can be maintained with necessary irreducible fine adjusting operation.</p> |
