A power amplifier drives a load connected to a first output terminal and a second output terminal. When generation of over-current is detected by the current detection section, the output amplifier control section is controlled to stop the operation of the output amplifier section, and when a voltage greater than or equal to said set value is detected by said voltage detection section, the stopped operation of said output amplifier section is maintained even though generation of the over-current is not detected at the current detection section. When the terminal voltage detection section detects a terminal voltage greater than or equal to a predetermined voltage, over-current at the current detection section is suppressed.