A low-power 3 V-5.5 V read/write preamplifier for rigid-disk drives

This read/write preamplifier for use with two-terminal thin-film or metal-in-gap (MIG) recording heads uses circuit approaches that drop supply voltage from 5 V to 3.3 V without sacrificing performance. In the write mode the preamplifier acts as a current switch with the write unsafe (WUS) detection circuitry activated. In the read mode it acts as a low-noise differential amplifier for reading sub-millivolt signals coming off the disk. In idle mode all circuits are shut down to reduce power dissipation to 1 mW. WUS circuitry provides write data protection in several cases: low write data input frequency, device in read or idle mode, and no write current. Data security is provided by the power supply fault-protection circuit that shuts down both read and write circuitry if the supply falls below 2.5 V.<>