Peter Real

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).

A wideband 10-bit, 20 Msps pipelined ADC using current-mode signals

A 10-b BiCMOS analog-to-digital converter (ADC) is used to demonstrate a current-mode pipeline system that overcomes some of the limitations of high-speed multiple-flash architectures. Although multistage ADCs are efficient in both die area and power, a track-and-hold amplifier (T/H) is required to prevent the input from changing while a conversion is taking place. If the ADC is pipelined (operating on more than one sample at a time), a T/H is required between each pipeline stage. Additionally, for resolution greater than about 8 b interstage amplification is required. The settling behavior of the T/Hs and amplifiers dominates the performance of these ADCs. To address these problems, a differential current-mode architecture incorporates current-mode T/Hs, obviating the need for interstage amplifiers. The prototype chip achieves 10 b of resolution at 20 Msample/s with an 80-MHz input bandwidth and dissipates 1 W.<<ETX>>