An amplifier device includes: a current amplifier element for amplifying an output current delivered to a capacitive load, such as, for example, a liquid crystal panel in dependency upon changes of the voltage of an input signal; an element for determining the state of changes in the input signal; and a control element for controlling the current amplifier element depending upon the state of changes in the input signal determined by the determination element in order to improve the output driving capability for the load. This amplifier device is applicable to an amplifier in a narrow sense and a buffer circuit in accordance with the mode of amplification. The former may include the configuration in which a second bias circuit for adding a bias current when the driving capability is required to be enhanced is provided in addition to an elementary bias circuit, and the configuration in which a first output drive element and the second output drive element and a plurality of output drive elements succeeding thereto are provided for additionally carrying out switching between incremental output currents. The latter may be classified into two types depending upon whether or not the potential difference element provided on the output side of the buffer circuit to detect a potential difference between the input and the output to add the output current when the the potential difference thus detected is above the threshold level.