A CMOS rectifier-integrator for amplitude detection in hard disk servo loops

In this paper a CMOS alternative amplitude detection system is presented. It is designed as an alternative for the, bipolar, amplitude detection in hard disk systems. The amplitude is detected by converting the input voltage to a current, rectifying the current, and integrating it on a capacitor. For this a new OTA topology and a rectifier cell are designed. This circuitry is expanded with a very linear current mirror and an automatic offset compensation system to cope with technology spread. The circuit was implemented in 1 ¿ CMOS. The measured accuracy is 0.2 % (9 bit).