An EER high frequency amplifier wherein the dynamic range of the gain can be widened by performing a predetermined control of a device in a high frequency amplifying part and thereby enhancing the isolation within the device. The length-changing actuator includes first and second ends. The contact at the tips 12 provides a damping effect. Adjoining current supply lines La are electrically connected to each other by a drain electrode of the luminescence driving transistor of the pixel positioned between these current supply lines La. The housing contacts slidably engage the parallel portions of the conductors and, as the housing is moved, the housing contacts slidably maintain electrical contact with the conductors.