A Low-Power, Compact, Adaptive Logarithmic Transimpedance Amplifier Operating Over Seven Decades of Current

This paper presents a detailed insight into the design space of wide-range transimpedance amplifiers enabling the design of micro-power, adaptive circuits for integrated current sensing applications. The analysis proves that the power dissipation of the nonadaptive structures varies linearly with dynamic range and quadratically with bandwidth. We present two adaptation techniques, modifying the bias current or output resistance, both of which alleviate this strong dependence on dynamic range. It is shown that adapting the bias current is most suitable for our application which requires a modest bandwidth but very wide dynamic range. Measurements demonstrate operation with currents ranging seven orders of magnitude from 200 fA to 2 muA with an average error of 0.8% and maximum error of 3.4%. The power consumption averaged over this entire range of currents is 3.45 muW . Either signal-to-noise ratio (SNR) or bandwidth can be made to tradeoff with the input current magnitude depending on the application. If the bandwidth is limited to 5 kHz, it achieves an average SNR of 65 dB.     

Model-based design of artificial zero power cochlear implant

This paper deals with a model-based design of an autonomous biomechatronic device for sensing and analog signal processing of acoustic signals. The aim is to develop a biomechatronic artificial cochlear implant for people with hearing loss due to damage or disease of their cochlea. The unique artificial electronic cochlear implant is based on an array of microelectromechanical piezoelectric membranes. Oscillations of membranes detect and filter acoustic signals in individual acoustic frequencies. The proposed biomechatronic device of the artificial cochlear implant consists of an active filters array, signal processing electronics, stimulation nerves electrodes and energy harvesting system for autonomous powering of the device. This solution differs from current cochlear implants solutions, which are bulky electronic systems limited by their high power consumption. The multidisciplinary models of the artificial cochlea implant concept are presented. The mechatronic approach based on model seems to be very useful for development of the full implantable cochlear implant which is designed for the sensing and processing of acoustic signals without external energy source.     

A micropower logarithmic A/D with offset and temperature compensation

Logarithmic circuits are useful in many applications that require nonlinear signal compression, such as in speech recognition front-ends (SRFEs) and cochlear implants or bionic ears (BEs). A logarithmic current-input analog-to-digital converter (A/D) with temperature compensation and automatic offset calibration is presented in this paper. It employs a diode to compute the logarithm, a wide linear range transconductor to perform voltage-to-current conversion, and a dual-slope auto- zeroing topology with 60 dB of dynamic range for sampling the envelope of speech signals. The temperature dependence of the logarithm inherent in a diode implementation is automatically cancelled in our circuit topology. Experimental results from a 1.5-/spl mu/m 3-V BiCMOS process show that the converter achieves a temperature stability lower than 150 ppm//spl deg/C from 12/spl deg/C to 42/spl deg/C, and consumes only 3 /spl mu/W of power when sampling at 300 Hz. At this level of power consumption, we show that the design is thermal-noise limited to 8 bits of precision. This level of precision is more than adequate for deaf patients and for speech recognition front-ends. The power consumption is almost two orders of magnitude lower than state-of-the-art DSP implementations, and the use of a local feedback topology achieves a 2.5-bit improvement over conventional dual-slope designs.     

A Bio-Inspired Active Radio-Frequency Silicon Cochlea

Fast wideband spectrum analysis is expensive in power and hardware resources. We show that the spectrum-analysis architecture used by the biological cochlea is extremely efficient: analysis time, power and hardware usage all scale linearly with $N$ , the number of output frequency bins, versus $Nlog(N)$ for the Fast Fourier Transform. We also demonstrate two on-chip radio frequency (RF) spectrum analyzers inspired by the cochlea. They use exponentially-tapered transmission lines or filter cascades to model cochlear operation: Inductors map to fluid mass, capacitors to membrane stiffness and active elements (transistors) to active outer hair cell feedback mechanisms. Our RF cochlea chips, implemented in a 0.13 $mu$m CMOS process, are 3 mm$,times,$ 1.5 mm in size, have 50 exponentially-spaced output channels, have 70 dB of dynamic range, consume $≪, $300 mW of power and analyze the radio spectrum from 600 MHz to 8 GHz. Our work, which delivers insight into the efficiency of analog computation in the ear, may be useful in the front ends of ultra-wideband radio systems for fast, power-efficient spectral decomposition and analysis. Our novel rational cochlear transfer functions with zeros also enable improved audio silicon cochlea designs with sharper rolloff slopes and lower group delay than prior all-pole versions.      

Low‐Power and High‐Contrast Nanoscale All‐Optical Diodes Via Nanocomposite Photonic Crystal Microcavities

A novel nanoscale integrated all‐optical diode is reported, realized by combining the strong plasmonic responses of gold nanoparticles with the all‐optical tunable properties of polymeric photonic crystal microcavities. Non‐reciprocal transmission properties are achieved based on the effect of surface‐plasmon resonance enhancing the optical non‐linearity and dynamic coupling of asymmetrical microcavity modes. An ultralow‐threshold photon intensity of 2.1 MW cm^?2 and an ultrahigh transmission contrast over 10⁴ are realized simultaneously. Compared with previously reported all‐optical diodes, the operating power is reduced by five orders of magnitude, while the transmission contrast is enlarged by three orders of magnitude.     

Threshold difference compensated sense amplifier

A dynamic flip-flop sense amplifier compensating for threshold difference between a pair of transistors by way of offset storage technique is presented. The DC and AC analyses on input offset voltage and performance limitations are discussed. Experimental results have shown that input offset is less than 2 mV with a 5 V single power supply, over a wide temperature range and a wide common mode input voltage range.     

Three-dimensional modeling and visualization of the cochlea on theInternet

3D modeling and visualization of the cochlea using the World Wide Web (WWW) is an effective way of sharing anatomic information for cochlear implantation over the Internet, particularly for morphometry-based research and resident training in otolaryngology and neuroradiology. In this paper, 3D modeling, visualization and animation techniques are integrated in an interactive and platform-independent manner and implemented over the WWW. L.T. Cohen et al.'s (1996) template shape with mean cross-sectional areas of the human cochlea is extended into a 3D geometrical model. Also, spiral computer tomography data of a patient's cochlea is digitally segmented and geometrically represented. The cochlear electrode array is synthesized according to its specification. Then, cochlear implantation is animated with both idealized and real cochlear models. The insertion length, angular position and characteristic frequency of individual electrodes are estimated online during the virtual insertion. The optimization of the processing parameters is done to demonstrate the feasibility of this technology for clinical applications     

Visualization of high dynamic range images

A novel paradigm for information visualization in high dynamic range images is presented in this paper. These images, real or synthetic, have luminance with typical ranges many orders of magnitude higher than that of standard output/viewing devices, thereby requiring some processing for their visualization. In contrast with existent approaches, which compute a single image with reduced range, close in a given sense to the original data, we propose to look for a representative set of images. The goal is then to produce a minimal set of images capturing the information all over the high dynamic range data, while at the same time preserving a natural appearance for each one of the images in the set. A specific algorithm that achieves this goal is presented and tested on natural and synthetic data.     

Study of the Acoustic Reflex Feedback Loop

The acoustic reflex is a regulator, which is thought to act as a protective mechanism in limiting the magnitude of high level sounds before they reach the cochlea.     

TRAPATT oscillations with a half-wave rectified sine wave current

TRAPATT oscillations in a p-i-n diode were simulated by an approximate but fast computer model. A diode current composed of the first two harmonics of a half-wave rectified sine wave gave high-efficiency oscillations over a wide range of current levels and over several orders of magnitude of the diode saturation current.     

Lumped-parameter model for in vivo cochlear stimulation

A lumped-parameter model that simulates the in vivo electrical properties of a guinea pig cochlea implanted with a multielectrode stimulating array is presented. A basic model of the low-frequency electroanatomy in a normally functioning guinea pig cochlea is developed by adding critical membrane capacitances to D. Strelioff's resistive network model (1973). The basic model of normal cochlear tissues is modified to account for anatomical and physiological differences between a normal and implanted cochlea, resulting in an impedance model of an implanted cochlea. Simulating the results of in vivo cochlear stimulation verifies the accuracy with which the modified cochlear model represents electrical properties within an electrically stimulated cochlea. Generalized simulations using this model suggest a straightforward phasing scheme capable of achieving sharply focused, channel-independent multielectrode cochlear stimulation     

Three-dimensional localization of cochlear implant electrodes using epipolar stereophotogrammetry

Three-dimensional (3-D) localization of individual cochlear implant electrodes within the inner ear is of importance for modeling the electrical field of the cochlea, designing the electrode array, and programming the associated speech processor. A 3-D reconstruction method of cochlear implant electrodes is proposed to localize individual electrodes from two X-ray views in combination with the spiral computed tomography technique. By adapting epipolar geometry to the configuration of an X-ray imaging system, we estimate individual electrode locations in the least square sense without using a patient attachment required by an existing stereophotogrammetry technique. Furthermore, our method does not require any knowledge of the intrinsic and extrinsic parameters of the imaging system. The performance of our method is studied in numerical simulation and with patient data and is found to be sufficiently accurate for clinical use. The maximum root mean-square errors measured are 0.0445 and 0.214 mm for numerical simulation and patient data, respectively.     

Precise wide-dynamic range constant current ratio circuits

A method of compensation of unequal VBE's in a conventional constant current ratio circuit is proposed, which improves the accuracy and the dynamic range of the current ratio considerably, without the need to use any higher resistance than normally desirable for integrated circuits. The linearity of the current ratio is better than 1 percent over a dynamic range of greater than four orders of magnitude.     

Two-terminal negative dynamic resistance

The letter describes a circuit which behaves as a 2-terminal negative dynamic resistance of a magnitude which is easily varied by an external resistor over a wide range.     

AlGaAsSb-InGaAsSb HPTs with high optical gain and wide dynamic range

Novel heterojunction phototransistors based on AlGaAsSb-InGaAsSb material systems are fabricated and their characteristics are demonstrated. Responsivity of a phototransistor is measured with applied bias voltage at four different wavelengths. The maximum responsivity around 1400 A/W and minimum noise equivalent power of 1.83/spl times/10/sup -14/ W/Hz/sup 1/2/ from this phototransistor with bias of 4.0 V at a wavelength of 2.05 /spl mu/m were measured at 20/spl deg/C and -20/spl deg/C, respectively. Noise equivalent power of the phototransistor is considerably lower compared with commercially available InGaAs p-i-n photodiodes. Collector current measurements with applied incident power are performed for two phototransistors. Currents of 400 nA at low intensity of 0.425 /spl mu/W/cm/sup 2/ and of 30 mA at high intensity of 100 mW/cm/sup 2/ are determined. Collector current increases nearly by five orders of magnitude between these two input intensities. High and constant optical gain of 500 in the 0.46-nW to 40-/spl mu/W input power range is achieved, which demonstrates high dynamic range for such devices at these power levels.     

A "divide and conquer" technique for implementing wide dynamic range continuous-time filters

This paper presents a technique for implementing analog filters with wide dynamic range and low power dissipation and chip area. The desired dynamic range of the filter is divided into subranges, each covered by a different filtering path optimized specifically for this subrange. This results in small admittance levels for the individual filtering paths and correspondingly small power dissipation and chip area. The system provides undisturbed output during range switching, contrary to conventional automatic gain control (AGC)/filter arrangements that generate disturbances every time the gain of the AGC changes. We also report on a low-noise highly linear CMOS transconductor useful for high-frequency applications. A chip implementing the ideas of this paper was fabricated in a 0.25-/spl mu/m digital CMOS process. The intended application of the filter is channel selection in an 802.11a/Hiperlan2 Wireless Ethernet receiver. The chip dissipates 9 mA, occupies an area of 0.7 mm/sup 2/, and maintains a signal/(noise + IM3 distortion) ratio of at least 33 dB over a 48-dB signal range, with good blocker immunity. This performance represents at least an order of magnitude improvement over existing channel selection filters, even those that do not achieve disturbance-free operation.     

A Soft Resistive Acoustic Sensor Based on Suspended Standing Nanowire Membranes with Point Crack Design

An artificial basilar membrane (ABM) is an acoustic transducer that mimics the mechanical frequency selectivity of the real basilar membrane, which has the potential to revolutionize current cochlear implant technology. While such ABMs can be potentially realized using piezoelectric, triboelectric, and capacitive transduction methods, it remains notoriously difficult to achieve resistive ABM due to the poor frequency discrimination of resistive‐type materials. Here, a point crack technology on noncracking vertically aligned gold nanowire (V‐AuNW) films is reported, which allows for designing soft acoustic sensors with electric signals in good agreement with vibrometer output—a capability not achieved with corresponding bulk cracking system. The strategy can lead to soft microphones for music recognition comparable to the conventional microphone. Moreover, a soft resistive ABM is demonstrated by integrating eight nanowire‐based sensor strips on a soft trapezoid frame. The wearable ABM exhibits high‐frequency selectivity in the range of 319–1951 Hz and high sensitivity of 0.48–4.26 Pa^?1. The simple yet efficient fabrication in conjunction with programmable crack design indicates the promise of the methodology for a wide range of applications in future wearable voice recognition devices, cochlea implants, and human–machine interfaces.     

Characterization of radiative efficiency in double heterostructures of InGaAsP/InP by photoluminescence intensity analysis

The photoluminescence (PL) intensity of an InGaAsP layer has been investigated as a function of excitation power density over a wide range of five orders. Two samples with n-InP/n-InGaAsP isotype and p-InP/n-InGaAsP heterotype doping have quite different excitation power dependences on PL intensity. The heterotype sample has notable nonlinear dependence. The excitation power dependences of PL intensity are theoretically analyzed. The estimated interface recombination velocity of the InP/InGaAsP heterojunction is found to be very low (smaller than a few cm/sec), compared with that of a GaAs/GaAlAs heterojunction.This PL intensity analysis has been applied to study the effect of an InP buffer layer and thermal degradation of radiative efficiency. The effective non-radiative recombination life time has been estimated as about 2×10⁻⁹ s for the double heterostructure with no buffer layer. Annealing in conditions of low phosphorus pressure leads to degradation of radiative efficiency, and the degradation is attributed to decrease in the nonradiative life time in the quaternary layer rather than increase in the interface recombination velocity. Sufficient phosphorus pressure prevents degradation of radiative efficiency. The correlation between PL intensity and output optical power of the light emitting diode has also been investigated. The PL intensity must be measured at high excitation power if it is to accurately predict the output power as a light emitting diode.     

A 144 × 144 Current-Mode Image Sensor With Self-Adapting Mismatch Reduction

We present a novel CMOS continuous-current imager that uses nonvolatile floating-gate charge storage in each pixel for automatic cancellation of fixed-pattern noise (FPN) and vignetting artifacts. We demonstrate the ability to reduce image artifacts over a wide range of incident light intensities. Adaptation occurs for each pixel in parallel, using a unique pixel circuit that employs hot-electron injection in stable feedback to accurately match a reference value. The adaptation mechanism stores a reference image, which may be uniform for FPN cancellation or nonuniform for various imaging applications. The design has been fabricated in a commercially available 3-metal, 2-poly 0.5-mum standard CMOS technology. Experimental results confirm the ability to reduce the FPN variance by a factor of 178x at the intensity at which adaptation was performed, and by a factor of 34x over five orders of magnitude of intensity. Adaptation takes as little as 4 s and the 144 times 144 image can be acquired at 0.9 frames/s. During normal operation, the chip consumes 140 muW under standard office lighting conditions at room temperature.     

Optical Amplifier Applications in Fiber Optic Local Networks

The number of waveguide tapsNthat a passive optical fiber bus can accommodate is typically quite low, due to significant attenuation of the signal in the taps and splices. In an effort to increaseNsubstantially, this paper investigates the potential use of optical amplifiers to boost the signal along the bus. An analysis is performed for both direct detection and heterodyne detection. Values ofNare determined for a wide range of system and device parameters, such as signal duration, amplifier noise bandwidth, and amplifier saturation power. It is found that the use of optical amplifiers can increaseNby at least an order of magnitude, and by as much as two orders of magnitude under many circumstances.