Nicola Guerrini

High-valued passive element simulation using low-voltage low-power current conveyors for fully integrated applications

In this brief, we describe how, using low-voltage low-power second-generation current conveyors, it is possible to simulate the frequency behavior of high capacitances and inductances by utilizing only elements suitable for an integrated implementation. The effect of current conveyor nonidealities has been taken into account. The simulated inductances and capacitances have been utilized, as an example, in the design of a fully integrated bandpass filter. PSPICE simulations, performed employing a standard CMOS technology (ALCATEL Mietec 0.5 /spl mu/m) and showing good performance of the presented circuits, are also reported.

An ultralow-power switched opamp-based 10-B integrated ADC for implantable biomedical applications

This paper describes an ultralow-power switched opamp-based integrated analog-to-digital converter (ADC) for cardiac pacemakers applications. The ADC consumption, measured on 10 chip samples and averaged, is 8.18 /spl mu/W (stand-by value: 1 nW) for the analog part and of 9.71 /spl mu/W (5 nW) for the digital one, using a supply battery of 2.8 V. The converter has a resolution of 10-b, its typical operating clock frequency is 32 KHz (2.9 KS/s sampling rate) and is able to reach the same resolution at 2 V (0.7 KS/s sampling rate), with a dissipation of 1 /spl mu/W and 1.3 /spl mu/W for analog and digital part, respectively.

Large area CMOS image sensors

CMOS image sensors, also known as CMOS Active Pixel Sensors (APS) or Monolithic Active Pixel Sensors (MAPS), are today the dominant imaging devices. They are omnipresent in our daily life, as image sensors in cellular phones, web cams, digital cameras, ... In these applications, the pixels can be very small, in the micron range, and the sensors themselves tend to be limited in size. However, many scientific applications, like particle or X-ray detection, require large format, often with large pixels, as well as other specific performance, like low noise, radiation hardness or very fast readout. The sensors are also required to be sensitive to a broad spectrum of radiation: photons from the silicon cut-off in the IR down to UV and X- and gamma-rays through the visible spectrum as well as charged particles. This requirement calls for modifications to the substrate to be introduced to provide optimized sensitivity. This paper will review existing CMOS image sensors, whose size can be as large as a single CMOS wafer, and analyse the technical requirements and specific challenges of large format CMOS image sensors.

A novel low-voltage low-power fully differential voltage and current gained CCII for floating impedance simulations

In this paper we present a new current-mode basic building block that we named voltage and current gained second generation current conveyor (VCG-CCII). The proposed active block allows to control and tune both the CCII current gain and the voltage gain through external control voltages. It has been designed, at transistor level in a standard CMOS technology (AMS 0.35@mm), with a low single supply voltage (2V), as a fully differential active block. The proposed integrated solution, having both low-voltage (LV) and low-power (LP) characteristics, can be applied with success in suitable IC applications such as floating capacitance multipliers and floating inductance simulators, utilizing a minimum number of active components (one and two, respectively). Simulation results, related to floating impedance simulators, are in good agreement with the theoretical expectations.

Vibration Damping Using CCII-Based Inductance Simulators

In this paper, we present an application of second- generation current-conveyor (CCII)-based active inductance simulators to mechanical vibration damping. The oscillation amplitude of a metallic beam, which is near some resonant frequencies, can be reduced by converting mechanical energy into electrical energy through a piezoelectric transducer that is bonded to the beam. An electric circuit, which is made up of the piezoelectric transducer, a resistance, and an inductance, accomplishes the task of dissipating the energy. To this end, the natural frequency of the circuit should be close to the natural frequency of interest of the mechanical system. The high value that is requested for the inductance (thousands of Henrys) can only be achieved through an inductance-simulator circuit. In the literature, the circuit implementations of the inductance simulators are typically based on operational amplifiers, such as the Antoniou circuit. In this paper, we make use of the CCIIs, which allow us to obtain both grounded and floating equivalent inductances that work within a regulated frequency range from three to four decades. The effectiveness of the traditional inductance simulators and CCII-based simulators is discussed, comparing the responses of an experimental mechanical-electrical system, with different circuit implementations, through experimental results. The use of series-resistance compensation, which is obtained through the use of a suitable topology based on the CCIIs, in the implementation of the equivalent inductance, allows one to obtain the best vibration damping, as confirmed by measurements, for all the natural mechanical frequencies of the realized system.

A novel CMOS temperature control system for resistive gas sensor arrays

A novel CMOS integrated system for the temperature control of resistive gas sensor interfaces is presented. It is formed by a sensor heater (which controls the sensor temperature), a resistance-to-frequency converter and digital control logic.

A temperature control system for integrated resistive gas sensor arrays

A temperature control system for integrated resistive gas sensor arrays is proposed. The circuit is a part of a portable system for ambient gas monitoring formed by a sensor array, the IC front-end, the temperature control system with the heater and the pattern recognition algorithm for the processing of the acquired data from the front-end. The sensors are arranged in order to detect a particular kind of gas among which CO2, CH4, H2 and SO2, through a 4-channel read-out front-end able to furnish the digital output signal. The temperature control is simplified by the presence of a second resistance matched with the sensor that operates as a thermal sensor. In this manner it is possible to control the sensor temperature without interference. The problem of the temperature control of the heater is reduced to the control of a resistance. The current (more generally the power) delivered to the heater resistance must be such that the temperature has to remain constant. This task is demanded to the second resistance, close to the heater one, that remains at the same temperature. Typically, such kinds of controls are implemented by topologies that maintain current sources or heater currents constant. In this work, the control circuit is able to maintain the power delivered to the heater resistance as constant.

Detector Developments at DESY

With the increased brilliance of state-of-the-art synchrotron radiation sources and the advent of free-electron lasers (FELs) enabling revolutionary science with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon sensitivity with low probability of false positives and (multi)-megapixels. At DESY, one ongoing development project - in collaboration with RAL/STFC, Elettra Sincrotrone Trieste, Diamond, and Pohang Accelerator Laboratory - is the CMOS-based soft X-ray imager PERCIVAL. PERCIVAL is a monolithic active-pixel sensor back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to preliminary specifications, the roughly 10 cm × 10 cm, 3.5k × 3.7k monolithic sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within 27 µm pixels to measure 1 to ∼100000 (500 eV) simultaneously arriving photons. DESY is also leading the development of the AGIPD, a high-speed detector based on hybrid pixel technology intended for use at the European XFEL. This system is being developed in collaboration with PSI, University of Hamburg, and University of Bonn. The AGIPD allows single-pulse imaging at 4.5 MHz frame rate into a 352-frame buffer, with a dynamic range allowing single-photon detection and detection of more than 10000 photons at 12.4 keV in the same image. Modules of 65k pixels each are configured to make up (multi)megapixel cameras. This review describes the AGIPD and the PERCIVAL concepts and systems, including some recent results and a summary of their current status. It also gives a short overview over other FEL-relevant developments where the Photon Science Detector Group at DESY is involved.

A 54mm x 54mm — 1.8Megapixel CMOS image sensor for medical imaging

A large area, 54 mm x 54 mm 1.8Megapixel CMOS image sensor was designed for scientific applications such as X-ray diffraction studies and direct medical X-ray imaging. Both applications have a requirement for large sensing area combined with a high dynamic range. The sensor was manufactured using stitching techniques in order to achieve a large, scalable design. The boundary between stitched sections is seamless, with no lost pixel space. Ten parallel outputs are used to enable a frame rate of up to 20 frames per second with full frame readout. Further increases in speed are possible by defining a region of interest.

10-th order programmable low-pass CMOS integrated pulse-shaping filter

In this paper we present the design of a 10-th order pulse shaping filter for QAM modems. The filter has been fabricated in a standard 0.35 /spl mu/m CMOS technology and shows a 37 MHz typical bandwidth with 1:4 tuning capability, more than 60 dB attenuation at twice the bandwidth, less than 1.4 dB pass-band ripple and good linearity in the phase response. Current consumption of the filter core is about 70 mA from a 3.3 V supply. Experimental results in good agreement with post-layout simulations are presented.