A 0.13-μm BiCMOS, 130-MHz Bandwidth Interface Circuit With Noise Canceling for HDD Fly-Height Resistive Sensors

A fully analog interface circuit based on closed-loop biasing and noise canceling techniques, fabricated in a 130-nm BiCMOS technology, is presented in this letter. The proposed interface circuit is able to precisely bias the sensor and read out the resulting signal in two frequency ranges (low-frequency (LF) range from dc to 375 kHz and high-frequency range from 1 kHz to 130 MHz). In the LF range, thanks to a dedicated noise-canceling technique, the achieved integrated input-referred noise is reduced from 7.3
$\mu \text{V}_{\mathrm{ rms}}$
to 2.8
$\mu \text{V}_{\mathrm{ rms}}$
in the 100-Hz to 1-kHz band and from 14.2
$\mu \text{V}_{\mathrm{ rms}}$
to 4.6
$\mu \text{V}_{\mathrm{ rms}}$
in the 1–100-kHz band, respectively. The fabricated chip features an active area of 1.11 mm2 and consumes 172 mW of power, including the 36 mW required to bias the sensor.