A CMOS RECTIFIER-INTEGRATOR FOR AMPLITUDE DETECTION IN HARD-DISK SERVO LOOPS

In this paper a CMOS alternative amplitude detection system is present ed, It is designed as an alternative for the, bipolar, amplitude detec tion in hard disk servo systems, The amplitude is detected by converti ng the input voltage to a current, rectifying the current, and integra ting it on a capacitor, For this a new OTA topology and a rectifier ce ll are designed, This circuitry is expanded with a very linear current mirror and an automatic offset compensation system to cope with techn ology spread, The measured accuracy of the amplitude detector is 0.2% (9 b), This makes the circuit suitable for implementation in state-of- the art hard disk systems with very high track densities and very shor t access times, Because the circuit is realized in standard CMOS its a further step toward CMOS only hard disk electronics, Because the circ uit operates from a single 3 V power supply and has limited power cons umption it can be used in battery powered systems.