According to the situation that the transistor output interface type of PLC output current is too small to meet requirements of high-speed, frequently on or off electromagnetic valve and other great current load drives, a current driver amplifier was developed which connected PLC output interface and load. Its key realization technologies include signal acquisition input, bidirectional conducting, input and output display, and designs of isolation circuit of input and output and output amplification processing circuit. The device uses bidirectional optocoupler and bidirectional LED to gather small DC current signal which does not distinguish between positive and negative polarities and achieve photoelectric isolation, controls drive load work of MOS transistor conducting and achieves current amplification through amplification driver link of emitter output, and has high frequently on-off operation, simple wiring, great drive current, strong versatility, high reliability and other characteristics.