The GMR preamplifier provides programmable read current / voltage bias and write current (5 bit DAC for the read bias, 5 bit DAC for the write current), fault detection circuitry and servo writing features. Read amplifier gain, write current wave shape (overshoot, undershoot and damping) can be adjusted and a thermal asperity detection and correction circuit can be enabled and programmed with different thresholds (6 bit DAC) through a 16-bit bi-directional serial interface (SDEN, SDATA, SCLK). The device operates from a +5V supply and a -5V supply (nominal). No external components are required as a trimmed or untrimmed resistor for reference current setting is employed.