MEMS Lorentz Force Magnetometers by Cesare Buffa

Author:Cesare Buffa
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

(6.1)

(6.2)

where and are voltage amplification of the two difference amplifiers and can be set using potentiometers (R d, 2, R d, 4) and are offset coefficients, again selectable through trimming resistors (not shown in this simplified schematic). Alternatively, offset voltages can be supplied using an analog output board controlled by LabVIEW software. The driving interface can be clearly used as single ended, either on actuation side 1 or on side 2, by suitably zeroing one of the potentiometers. The selected operational amplifier for these stages is the OPA445 by Texas Instruments, capable of standing up to 90 V of differential voltage supply with a good temperature immunity (typical offset drift ≈ 25 μV/∘C) and a fast slew rate (15 V∕μs). Such a large voltage supply range allows the test of very different kinds of devices. A fast slew rate is also required when it is required to apply large step or impulse voltages to the device (these stimuli are not instantaneous as in the ideal situation: yet they should be much faster than the M/NEMS mechanical bandwidth to be measured). Two switches allow to apply an offset voltage only (with no sine stimulus) at one side, while the sine stimulus is still applied at the other side.

Fig. 6.3Electronic schematic of the driving stage: two amplifiers generate amplified output signals with a 180∘ phase difference. The gain and offset of the signals can be selected through the trimming resistors

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