Hi-speed preamplifier write driver for hard drive with improved symmetry

摘要

A write driver ( 38 ) produces balanced voltages across head ( 32 ) by using the input write data (WDX and WDY) drive transistors of a slower transistor type (typically PNP) on one half of an H-bridge configuration, while transistors of a faster transistor type (typically NPN) in the other half of the H-bridge configuration are driven indirectly by transistors of the slower type, with a trans-resistance in series with transistors of the faster type. Accordingly, the voltage nodes on either side of the write head are pulled to Vcc and Vee symmetrically. A trans-resistance block ( 40 ) uses current sources to pull current from capacitive nodes for faster switching.