150 MHz Preamplifier for Magneto-Resistive Heads

This paper presents the read section of a 10-channel preamplifier for hard-disk-drive applications that use magneto-resistive-read/inductive-write heads. Ten dedicated low-noise amplifier stages use a current-bias current-sense architecture with grounded magneto-resistive (MR) heads. The amplifier also contains gain stages common to all heads, a high-frequency gain-boost, an MR bias current-DAC and a serial interface to program the IC. The preamplifier is designed in a 2.5 μm BiCMOS technology. Measurements using a single supply voltage of 3.8-5.5V show a -3 dB bandwidth of 120 MHz (without gain-boost) up to 180 MHz (with some gain-boost) and an input referred noise of 0.9 nV/ȚHz.