The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60−210 μm wavelength regime. In photometry mode, it simultaneously images two bands, 60−85 μm or 85−125 μm and 125−210 μm, over a field of view of ∼1.75 × 3.5 , with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47 × 47 , resolved into 5 × 5 pixels, with an instantaneous spectral coverage of ∼ 1500 km s −1 and a spectral resolution of ∼175 km s −1 . We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the performance verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions. Key words. space vehicles: instruments -instrumentation: photometers -instrumentation: spectrographsHerschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Palladium nanowires were fabricated on silicon substrates using conventional microfabrication techniques. Sensors based on such nanowires show a reversible response to hydrogen concentrations as low as 27 ppm with response times varying from 5 s (H2 concentrations >20%) to 30 s (H2 concentrations <100 ppm) at room temperature. The response times can be reduced by increasing the applied bias due to resistive heating. The noise spectrum of the nanowires shows a 1/f behavior, sufficiently low to enables the detection of hydrogen with an ultralow-power consumption. The influence of oxygen on the nanowire response was also investigated.

There is a growing demand for low-power, small-size and ambulatory biopotential acquisition systems. A crucial and important block of this acquisition system is the analog readout front-end. We have implemented a low-power and low-noise readout front-end with configurable characteristics for Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) signals. Key to its performance is the new AC-coupled chopped instrumentation amplifier (ACCIA), which uses a low power current feedback instrumentation amplifier (IA). Thus, while chopping filters the 1/f noise of CMOS transistors and increases the CMRR, AC coupling is capable of rejecting differential electrode offset (DEO) up to 50 mV from conventional Ag/AgCl electrodes. The ACCIA achieves 120 dB CMRR and 57 nV/ Hz input-referred voltage noise density, while consuming 11.1 A from a 3 V supply. The chopping spike filter (CSF) stage filters the chopping spikes generated by the input chopper of ACCIA and the digitally controllable variable gain stage is used to set the gain and the bandwidth of the front-end. The front-end is implemented in a 0.5 m CMOS process. Total current consumption is 20 A from 3V.

A crucial and important part of a medical diagnostics system is the monitoring of the biopotential signals. This paper describes a complete low-power EEG acquisition ASIC that is suitable for miniaturized ambulatory EEG measurement systems. The aim is not only to improve the patients' comfort but also to extend the device applications. Figure 8.2.1 shows the architecture of the EEG acquisition ASIC, which is implemented in a 0.5µm CMOS process. It consists of eight readout channels, an 11b ADC, a square-wave oscillator and a bias circuit. In addition to the acquisition mode, the ASIC has calibration and impedance measurement modes.The EEG signals are µV-range low-frequency signals that are correlated with a large amount of common-mode (CM) interference. Therefore, a low-noise and high-CMRR amplifier is necessary, for which chopping is commonly used [1]. However, the differential electrode offset (DEO) voltage between the biopotential electrodes requires filtering prior to amplification. The AC-coupled chopperstabilized instrumentation amplifiers (ACCIA) can achieve high-CMRR and eliminate 1/f noise, while filtering the DEO by using a DC servo-loop outside the choppers that introduces a high-pass filter (HPF) characteristic [2,3]. The implementation in [3] however, has a low input impedance (7.5MΩ), which is suitable for implantable applications but does not meet the expectations of regular clinical EEG systems (100MΩ) [4]. In contrast, the system described in [2] meets the requirements for clinical EEG but has worse power-noise performance than [3]. Figure 8.2.2 shows the concept and the implementation of the proposed ACCIA.The servo-loop is divided into a coarse low-pass filter (LPF) with discrete output levels and a fine LPF with a continuous output range to mimic the operation of a single servo-loop with a continuous output range. The core amplifier is a current balancing IA (CBIA) similar to [2] that is followed by a gain stage. If the current through R 1 due to the DEO can be supplied by the fine-coarse servo-loop, which consists of an integrator, a coarse transconductance (CGM) and a fine transconductance (FGM), the DEO can be filtered. Thanks to the CGM, the FGM does not need to supply all the current for the specified DEO range, which reduces its power dissipation significantly compared to [2]. The CGM uses two comparators to periodically check whether the FGM has reached its limit and to control the current DAC. However, a critical concern about the fine-coarse operation of the servo-loop is the steering of the current DAC of the CGM stage since a conventional DAC will create voltage steps at the output of the ACCIA during every DAC bit change. Therefore, the steering time-constant of the DAC must be much smaller than (1/2πf HP ) so that the FGM can suppress the artifact by adjusting its output (f HP is the HPF cut-off frequency of the ACCIA set by the fine servo-loop).Figure 8.2.3 shows the "slow-DAC" implementation. The transistors M 1 and M 2 serve as pass-gates. The output current measurement of a cu...