Magnetic recording channel front-ends

Readback front-end electronics for both inductive and magnetic recording (MR) heads are investigated. For inductive front-ends, it is shown that the channel bandwidth is determined by the transfer of the induced head voltage to the front-end input terminals. The parameters limiting this bandwidth are calculated. A noise analysis shows that the signal-to-noise ratio can be optimized and gives the parameter values for which this happens. The effect of noise matching of the head to the front-end is demonstrated. For MR front-ends the principles of auto bias and relative resistance sensing are presented. Front-end configurations producing voltage biasing and current biasing are discussed. Two examples of signal conditioning in MR front-ends are given: an on-the-chip equalizer compensating the frequency roll-off introduced by the head cable inductance, and a signal-adaptive circuit for removing thermal asperities