In 1969, Hitachi introduced the first vertical power MOSFET,[6] which would later be known as the VMOS (V-groove MOSFET).[7] From 1974, Yamaha, JVC, Pioneer Corporation, Sony and Toshiba began manufacturing audio amplifiers with power MOSFETs.[8] International Rectifier introduced a 25 A, 400 V power MOSFET in 1978.[9] This device allows operation at higher frequencies than a bipolar transistor, but is limited to low voltage applications.