Write driver design considerations for high-frequency rigid disk recording

Prior reported PSPICE modeling work has demonstrated subnanosecond field ri se-times for a head driven by an ideal current source. Results including th e flexure interconnection have demonstrated 1 ns field rise-times without p ulse distortion. Three write driver designs are explored. A simple H-bridge , an H-bridge with fly-over diodes, and an H-bridge with clamped transistor s to improve switching speed are compared. The driver models are implemente d using BJTs with state-of-the-art industry MOSIS process model parameters for PSPICE. The simulations show that for the low inductances considered an d the relatively high supply voltage employed, the fly-over diodes are not required. The H-bridge with clamped transistors is the fastest driver (50 O mega resistive load) but suffers from a limited current capability for the small transistor areas required for high speed. The driver designs are rest ricted by termination requirements which generally do not correspond to opt imum switching times for the 50 Omega resistive load used for preliminary e valuation. Finally, by reducing the interconnection length to 25 mm, stacki ng the head turns, and using the simple H-bridge driver, it is demonstrated that a field rise-time of less than 0.2 ns can be achieved. The resulting waveform is presented and the implications discussed. (C) 2000 American Ins titute of Physics. [S0021-8979(00)58608-3].