Low distortion audio range class-AB full H-bridge pre-driver amplifier

A circuit for providing drive voltages to a voice coil motor (VCM), said circuit having two driver sets, each driver set including a high and a low side driver, each driver set for connection to respective opposite sides of said VCM, each driver set comprising:

• first and second SENSEFETs respectively in said high and low side drivers, each SENSEFET having a power FET portion for selectively connecting a side of said VCM to a driving voltage potential and a sense FET portion for sensing a sense current in said power FET portion;
• means for developing a sense voltage proportional to said sense current sensed by said sense FET portion of said SENSEFET of said low side driver;
• means for increasing a gate bias on gates of said SENSEFET of said low side driver when said sense current falls below a predetermined level;
• and
• means for driving a predetermined current in said power FET portion of said SENSEFET of said high side driver when said sense current falls below said predetermined level, wherein at least about said predetermined current flows in said SENSEFETs at least during a switchover from a high side driver to a low side driver in one of said driver sets.

A mass data storage device, comprising:

• a circuit for providing drive voltages to a voice coil motor (VCM), said circuit having two driver sets, each having a high and a low side driver, each driver set for connection to respective opposite sides of said VCM, each driver set comprising:
• first and second SENSEFET devices respectively in said high and low side drivers, each SENSEFET device having a first portion for selectively connecting a side of said VCM to a VCM driving potential and a second portion for sensing a current in said first portion;
• a circuit for developing a sense voltage proportional to a sense current sensed by said second portion of said SENSEFET device of said low side driver;
• a circuit for increasing a gate bias on gates of said SENSEFET device of said low side driver when said sense current falls below a predetermined level;
• and
• a circuit for driving a predetermined current in said SENSEFET device of said high side driver when said sense current falls below said predetermined level, wherein a current of at least about said predetermined level always flows in said SENSEFET devices.