150 Mb/s Write Amplifier for Hard Disk Drives with Near Rail-to-Rail Voltage Swing

An integrated write amplifier meant for use with magneto-resistive (MR)-read/inductive- write heads is presented. To achieve short rise- and fall-times, it incorporates near rail-to-rail output voltage swing using a NPN-VPNP push-pull output stage combined with common mode control. After deriving some physical lower limits for rise- and fall-times, the main circuit principles are explained. The circuits have been used successfully in a 10 channel, 5 Volt MR-read/inductive-write amplifier.