The piezoelectric stack actuators typically employed in nanopositioning are highly capacitive and, due to their frequency-dependent behaviour, place extreme demands on the drive electronics, especially in high-bandwidth operation. Typical commonly-available amplifiers target purely resistive or negligibly-reactive loads, rendering them unsuitable for such applications. The few commercially-available devices that can drive such actuators are, due to the limitations of conventional power amplification schemes, largely limited in one or more of the following required performance characteristics: wide load-capacitance range, high output current, high power bandwidth, and low output noise. This article presents a battery-based power amplification topology that has the advantage of being able to stably supply high currents at virtually zero noise over large bandwidths, readily bridging the triad of high current, high bandwidth, and low noise. A linear scheme applicable to a wide load-capacitance range, and stable, oscillation-free operation is realized with minimal bandwidth loss by implementing suitable frequency compensation. The system has the added advantage that the voltage and current capacities can be easily scaled up by simply adding more battery cells. The developed prototype demonstrates a significant improvement in performance compared to the state-of-the-art, and simultaneously achieves high power (150 V, 3.30 A rms) and low noise (max. 3.51 mV, 700 kHz bandwidth) for a wide range of loads. The power bandwidth is 5 kHz (1 uF load) while the small-signal bandwidth is 700 kHz.

Nanometer-resolution position sensing is a critical requirement in several precision applications such as Atomic Force Microscopy (AFM), especially over large bandwidths. Giant magnetoresistance-based (GMR) sen?sors have shown great promise for this; however, they exhibit significantly higher 1/f noise even over large band?widths, which limits the achievable SNR. Therefore, the sensing system needs to be designed at the system-level in order to minimize excess intrinsic noise generation and transmission, as well as external noise pickup. This article, both analytically and experimentally, investigates the noise characteristics of the GMR sensor and its readout circuit components, and their effect on SNR. A general process for designing a low-noise high-bandwidth readout circuit, applicable not just to GMR sensors but also to other high?1/f-noise sensors, is presented. A resolution of 2.5 nm over a bandwidth of 100 kHz is demonstrated on an AFM nanopositioner, a ten-fold improvement over previously reported performance and comparable to other state-of?the-art, but more complex, position sensing schemes. The readout scheme is simple to implement using COTS com?ponents and easily extendable to higher bandwidths, unlike other schemes, such as modulation/demodulation, where the requirement for increasingly higher carrier frequencies renders further improvements in bandwidth impractical.