Amplifier device capable of realizing high slew rate with low power consumption

An amplifier device capable of performing an efficient amplifying operation with a low power consumption, comprising:

• amplifier circuit means at least having an input amplifier stage which amplifies a level change of an input signal, and an output stage which outputs an amplified current as a driving output to a capacitive load;
• primary bias means for ordinarily supplying a main fixed bias current to said amplifier circuit means;
• determination means for determining a change condition of said level change of the input signal, which is supplied from said input amplifier stage, so as to generate a control signal corresponding to said change condition;
• and
• driving capability increase means as secondary bias means for increasing a total bias current at least by supplying said total bias current to said input amplifier stage thereby changing an output issued from said input amplifier stage in order to increase said driving output supplied to said capacitive load when said control signal is input.