Marvell International Limited

Zhiliang Zheng

Steven C Lam

A CMOS differential amplifier is provided comprising a current supply coupled to a first terminal of a power supply. A first CMOS transistor is provided having a first source, a first gate, and a first drain coupled to the current supply. A second CMOS transistor is also provided having a second source, a second gate, and a second drain coupled to the current supply. The first and second gates are inputs to the CMOS differential amplifier. A resistance is coupled between a second terminal of the power supply and the first source of the first transistor and the second source of the second transistor to improve common-mode and ground noise suppression.

Efficient ground noise and common-mode suppression network

A multi-stage amplifier having a plurality of switch mechanisms, one for each stage, that are individually controllable to vary the gain of the amplifier without compromising bandwidth. The amplifier may be embodied in a magnetic storage medium magnetic storage medium that includes a preamplifier in which the multi-stage amplifier is embodied.

Constant bandwidth, variable gain amplifier, and method

In this invention an integrated operational amplifier is calibrated to optimize phase margin. The calibration is done to correct changes caused by operating temp and supply voltages as well as process variations and aging that can affect the stability of the amplifier. A calibration circuit measures the response of the operational amplifier to a pulse input and controls a feedback impedance to produce an optimized phase margin. The output response to the pulse input is measured at two different times, at a first time close to the transition capturing the peak overshoot from an under damped amplifier and at second time later than the first measurement when the distortions from the under damped ringing have diminished. A quantizer circuit compares the two measure voltages and provides an input to control logic which selects the amount of reactance in the feedback of the operational amplifier. The calibration terminates when the dampening of the amplifier has reached the least significant bit of adjustment available to the calibration process.

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San Jose, CA, United States of America

Zhiliang Zheng