Abstract: A servo system for controlling the position of a read/write head in a disk drive is provided. The servo system includes an input terminal for sequentially receiving a plurality of input signal bursts of a burst pattern, wherein the input signal bursts include positional information of the head. Demodulation circuitry, coupled to the input terminal, sequentially demodulates each input signal burst and provides a demodulated signal for each burst. An ADC, coupled to the demodulation circuitry, sequentially converts each demodulated signal. The ADC converts a first demodulated signal corresponding to the first of the plurality of input signal bursts before the demodulation circuitry completes demodulating the next of the plurality of input signal bursts. In a preferred embodiment, the ADC converts a demodulated signal corresponding to a first input signal burst while the demodulation circuitry demodulates a signal corresponding to a second, and subsequent, input signal burst.

Abstract: A comparator for use in an A/D converter such as an algorithmic type. The circuit includes a push-pull inverter gain stage having two series-connected MOSFETs. The input of this inverter is driven by a signal from a preceding current-comparison stage where an input current is compared to a reference current to set the signal level on an input node of the inverter. The trigger point of the inverter is altered by an additional MOSFET, connected in parallel with one of the inverter MOSFETs, and having its gate controlled by the output of a bias voltage control circuit. This circuit includes a control inverter stage matched to the comparator inverter and driven by a control current-comparison circuit matched to the corresponding comparator current-comparison circuit.