Msj. Steyaert et al., A CMOS RECTIFIER-INTEGRATOR FOR AMPLITUDE DETECTION IN HARD-DISK SERVO LOOPS, IEEE journal of solid-state circuits, 30(7), 1995, pp. 743-751
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.