Gain Control Circuitry Research Articles

Spiking Cochlea With System-Level Local Automatic Gain Control

Including local automatic gain control (AGC) circuitry into a silicon cochlea design has been challenging because of transistor mismatch and model complexity. To address this, we present an alternative system-level algorithm that implements channel-specific AGC in a silicon spiking cochlea by measuring the output spike activity of individual channels. The bandpass filter gain of a channel is adapted dynamically to the input amplitude so that the average output spike rate stays within a defined range. Because this AGC mechanism only needs counting and adding operations, it can be implemented at low hardware cost in a future design. We evaluate the impact of the local AGC algorithm on a classification task where the input signal varies over 32dB input range. Two classifier types receiving cochlea spike features were tested on a speech versus noise classification task. The logistic regression classifier achieves an average of 6% improvement and 40.8% relative improvement in accuracy when the AGC is enabled. The deep neural network classifier shows a similar improvement for the AGC case and achieves a higher mean accuracy of 96% compared to the best accuracy of 91% from the logistic regression classifier.

A 2.64- μW 71-dB SNDR Discrete-Time Signal-Folding Amplifier for Reducing ADC's Resolution Requirement in Wearable ECG Acquisition Systems.

This paper presents the design of a low-power discrete-time signal-folding amplifier intended for use in place of programmable-gain amplifiers (PGA) in electrocardiogram (ECG) acquisition systems. The amplifier provides a fixed high gain while preventing output signal saturation even with rail-to-rail inputs, thanks to the proposed discrete-time signal folding technique; the fixed gain eliminates the need of gain-control circuitry while the high gain helps relax the resolution requirement of the analog-to-digital converter (ADC) that follows, thus resulting in lower power consumption and design complexity for the ADC. Fabricated in a standard 0.18- μm CMOS process, the amplifier occupies an active area of 0.254 mm2 and consumes 2.64 μW from a 1.2-V supply voltage. While amplifying a rail-to-rail input (2.4 Vpp differential) with a gain of 17.8V/V, the amplifier achieves a signal-to-noise-plus-distortion ratio (SNDR) of 71dB, thus making it very attractive for high-fidelity ECG recording amid large input interferences.

Differential Phase Measurement Accuracy of a Monobit Receiver

Differential phase measurements using two receiver channels are used to calculate the angle of arrival of a target signal. A monobit receiver architecture is a desirable receiver type due to its low hardware complexity, sampling rate, and power efficiency. The application motivating this paper benefits from the use of automatic gain control circuitry and sensitivity offered by the monobit architecture. However, the one-bit sampling of the input signal introduces undesirable non-linear effects. This paper analyzes the effects of a monobit receiver architecture on the differential phase accuracy. Simulated results are compared to measurement data collected from prototype monobit receiver hardware. The measured data had good agreement with the simulated results. At a high-input signal-to-noise ratio of 30 dB, the differential phase measurement sigma was approximately 0.66° for input phase shifts of 0°, 45°, and 90°. While the differential phase measurement accuracy is less than predicted by the Cramer–Rao lower bound, it is sufficient for the low cost, power, and size constrained sensor application motivating this paper.

8 Gbits/s inductorless transimpedance amplifier in 90 nm CMOS technology

This work presents the design and the measured performance of a 8 Gb/s transimpedance amplifier (TIA) fabricated in a 90 nm CMOS technology. The introduced TIA uses an inverter input stage followed by two common-source stages with a 1.5 k? feedback resistor. The TIA is followed by a single-ended to differential converter stage, a differential amplifier and a 50 Ω differential output driver to provide an interface to the measurement setup. The optical receiver shows a measured optical sensitivity of ?18.3 dBm for a bit error rate = 10?9. A gain control circuitry is integrated with the TIA to increase its input photo-current dynamic range (DR) to 32 dB. The TIA has an input photo-current range from 12 to 500 μA without overloading. The stability is guaranteed over the whole DR. The optical receiver achieves a transimpedance gain of 72 dBΩ and 6 GHz bandwidth with 0.3 pF total input capacitance for the photodiode and input PAD. The TIA occupies 0.0036 mm2 whereas the complete optical receiver occupies a chip area of 0.46 mm2. The power consumption of the TIA is only 12 mW from a 1.2 V single supply voltage. The complete chip dissipates 60 mW where a 1.6 V supply is used for the output stages.

Removing non-stationary noise in spectrum sensing using matrix factorization

Spectrum sensing is key to many applications like dynamicspectrum access (DSA) systems or telecom regulators who need to measure utilization of frequency bands. The International Telecommunication Union (ITU) recommends a 10 dB threshold above the noise to decide whether a channel is occupied or not. However, radio frequency (RF) receiver front-ends are non-ideal. This means that the obtained data is distorted with noise and imperfections from the analog front-end. As part of the front-end the automatic gain control (AGC) circuitry mainly affects the sensing performance as strong adjacent signals lift the noise level. To enhance the performance of spectrum sensing significantly we focus in this article on techniques to remove the noise caused by the AGC from the sensing data. In order to do this we have applied matrix factorization techniques, i.e., SVD (singular value decomposition) and NMF (non-negative matrix factorization), which enables signal space analysis. In addition, we use live measurement results to verify the performance and to remove the effects of the AGC from the sensing data using above mentioned techniques, i.e., applied on block-wise available spectrum data. In this article it is shown that the occupancy in the industrial, scientific and medical (ISM) band, obtained by using energy detection (ITU recommended threshold), can be an overestimation of spectrum usage by 60%.

Active Crossover For Use With Multi-Driver Headphones

A headset with an active crossover network is provided. The headset is coupled to an audio source using either a wired connection or a wireless connection. The active crossover network, utilizing either analog or digital filtering, divides each channel of the incoming audio signal from the audio source into multiple frequency regions sufficient for the number of drivers contained within each headphone of the headset. The output from the network's filters is amplified using either single channel or multi-channel amplifies. Preferably, gain control circuitry is used to control the gain of the amplifier(s) and thus the volume produced by the drivers. More preferably, the gain of the gain control circuitry is adjustable. The headset includes a power source that is coupled to the amplifier(s) and, if necessary, the network's filters. The power source can be included within some portion of the headset or included within a wireless interface. Alternately, an external power source can be used, for example one associated with the audio source.

A low-power integrated tuner for cable telephony applications

This paper describes an integrated tuner for cable telephony in a 0.35 /spl mu/m, 27 GHz SOI BiCMOS technology. The IC integrates a complete dual-conversion signal path including upconverter, downconverter, variable-gain amplifier, LO synthesizers with fully integrated voltage-controlled oscillators, gain control circuitry, as well as digital calibration and interface circuits. It accepts signals in the 200-880 MHz band and produces a 44 MHz IF. Drawing 168 mA from a 3 V supply, the tuner system has a worst case noise factor of 7.3 dB, system phase noise below -78 dBc/Hz at a 10 kHz offset, spurs below -42 dBc for 137 5 dBmV input channels, a gain of 60 dB, and gain control range of 68 dB. The 13 mm/sup 2/ IC meets specifications across an outdoor temperature range of -40/spl deg/C to 100/spl deg/C in production lots.

An iterative energy-centroid method for recalibration of PMT gain in PET or gamma camera

In gamma and positron emission tomography cameras, photomultiplier tubes (PMT) are still the most popular photosensors. Gain uniformity of the PMTs in these instruments is very important for preventing degradation in image resolution and distortion. When an Anger decoding detector head is exposed to a uniform flood source without lead collimation, the energy spectrum acquired by any single PMT has no photopeak for conducting recalibration. A method using the centroid of a wide energy spectrum even without photopeak as a gain-tuning index is presented in this paper. With a uniform flood illumination, without collimation, the gain equalization of PMTs within an array can be tuned to its initial level by an iterative centroid match. If an electrically adjustable gain control circuitry such as tunable PMT high-voltage or variable-gain amplifier is applied, the recalibration can be done automatically with this method. Our experiments demonstrated a 2.5%-3% gain accuracy that is enough to eliminate distortion in total energy and two-dimensional decoding. Counting efficiency increases significantly, and the calibration or system-tuning time will be shortened because of efficiency improvement.

A variable gain amplifier with 50-dB control range for 900-MHz applications

A variable gain amplifier for 900-MHz applications has been designed and fabricated in a BiCMOS process with f/sub T/ = 24 GHz. The amplifier has linear-in-dB gain control with a 50-dB control range. The maximum gain is 28 dB and the third-order output intercept point (OIP3) is 13.7 dBm. The gain is achieved in one gain stage with a cascoded output. The amplifier bias network and the gain-control circuitry are temperature compensated for temperature-independent gain at any gain setting. The bias network also uses a feedback loop to cancel out undesired low frequencies present at the radio-frequency input. The maximum output power is +10 dBm and the output 1-dB compression point is +8.7 dBm. Active chip area is 0.1 mm/sup 2/. The amplifier is packaged in a SOT-363 and consumes 30 mA from a 2.8-V supply.

A 2.7-5.5 V, 0.2-1 W BiCMOS RF driver amplifier IC with closed-loop power control and biasing functions

A 800-900 MHz BiCMOS driver amplifier with 30 dB gain is integrated with various functions of a power control loop which includes a peak power detector, an integrator filter, gain control circuitry, and a voltage regulator for biasing a discrete power device. To add to its versatility, the IC is pad-programmable to deliver either 0.25 W/0.5 W/1.0 of RF power while maintaining a power added efficiency of 35 to 40% in each case. This has been shown to be useful in creating 1-4 W power amplifier solutions with over 50% efficiency. In closed-loop configuration, this IC provides better than 1 dB of output power control over a dynamic range of 25 dB.

A BiCMOS Differential Amplifier and Timing Discriminatorfor the Receiver of a Laser Radar

A differential BiCMOS amplifier channel with gain control circuitry and a timing discriminator has been designed for a pulsed time-of-flight laser radar. The measured bandwidth of the amplifier cha...

Solid state audio amplifier emulating a tube audio amplifier

A solid state audio amplifier for connection with a loudspeaker cabinet or emulation thereof to provide amplification characteristics emulating in frequency response those of a valve audio amplifier driving a loudspeaker cabinet. The loudspeaker cabinet comprises a loudspeaker drive and its enclosure. The frequency response of the audio amplifier exhibits a low frequency resonant peak in gain representing the fundamental resonance of the loudspeaker cabinet and a monotonic increase in gain at higher frequency associated with the impedance provided voice coil inductance of the loudspeaker cabinet. The audio amplifier comprises an amplifier and gain control circuitry associated therewith. The amplifier comprises a differential amplifier and the gain control circuitry comprises a impedance network connected in feedback. The impedance network comprises a tuned circuit connected to create the low frequency resonant peak in gain and a reactance providing the increase in gain at higher frequency. The tuned circuit comprises a capacitance and a gyrator circuit simulating an inductance and the reactance comprises a capacitance.

Multichannel PC-based data-acquisition system for high-resolution EEG.

This paper describes a complete, high-performance data-acquisition system for high-resolution EEG. The system includes preamplified EEG electrodes, rigid helmets, differential instrumentation and software-controlled gain amplifiers, digitizing and control circuitry, and optical coupling to a 486 PC. Miniaturized preamplifiers mounted on individual electrodes reduce coupling to external electromagnetic fields and minimize signal distortion caused by increased and/or imbalanced electrode impedances. Electrodes are applied quickly and with minimal skin preparation, yet with high packing densities and repositioning consistent to about 1-3 mm in repeated applications. Extensive testing under realistic conditions demonstrates that the system provides superior electrical performance compared to currently available commercial systems.

Digital correlators for synthetic aperture interferometric radiometry

A numerical simulator is developed to assess various design implications of a digital correlator used by a synthetic aperture interferometric radiometer (SAIR). The simulator permits control of the type of digitization, the digitization thresholds with respect to noise power, and the degree of correlation between the two antenna signals which are being cross correlated. Digitization schemes are considered which use 2, 3, 4, and 8 levels. Estimates are made of the increase in inherent radiometer noise (/spl Delta/T) due to the digitization. The increase in /spl Delta/T is found to depend strongly on the degree of correlation, with higher correlations suffering less increase. In most cases, 3 level digitization is recommended based on this sensitivity consideration. Two levels perform significantly noisier and four levels only slightly cleaner. Several case studies are also considered regarding the need to control the signal level relative to the digitizer thresholds. Automatic gain control circuitry prior to digitization is found not to be necessary, provided the thresholds are preset within a fairly broad region of minimum sensitivity to variations in signal power, and provided the system noise temperature of the radiometer is monitored with reasonable accuracy. It is also found that, under conditions of very high correlation between the two signals, digital correlators have better SNR performance than analog. Reasons for this behavior are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A 50-MHz CMOS amplifier channel for a laser radar

An integrated CMOS amplifier channel consisting of a transimpedance preamplifier, postamplifiers, and gain control circuitry has been designed for the receiver of a pulsed time-of-flight laser radar. The measurement results, a total transimpedance ofZt ≈ 250 kΩ with a bandwidth ofBW ≈ 65 MHz and an input-referred noise current ofini ≈ 7 pA/√Hz, show that a range measurement resolution of centimeter/decimeter class could be achieved by detecting the edge of the received laser pulse.

Automatic camera gain and pedestal control for adaptive scene contrast enhancement

A mechanism is presented to achieve adaptive scene contrast enhancement-a common problem in TV and IR imager,j applications-by controlling camera gain and pedestal in an automatic fashion. The goal of adaptivity, in a precise meaning, is "content windowing" where image signals are selectively extracted and contrast enhanced, probably with respect to both dynamic-range compression and expansion. We adopt the image-analysis strategy, distinct from classical electronic methods (e.g., automatic gain control circuitry), such that the overall behavior of frame pixels (e.g., image histogram) is optimized for feedback control of camera gain and pedestal in a live video process. The video formation process is linearly modeled so that we can derive an automatic control fashion to meet the proposed image-quality criterion, which is naturally simple and flexible for practical use in a variety of applications. Experiments show that our method adapts well in dynamic environments and can be easily hardware implemented.

Noise reduction system

Electronic circuitry as described which enhances the intelligibility of a speech signal corrupted by low-frequency noise while tending to retain frequency components of the signal characteristic of natural-sounding speech. The circuitry includes a broad band channel which passes the speech signal with little spectral distortion. A high-pass channel produces a high-pass signal corresponding to high-frequency components of the speech signal, components which in themselves provide the human ear with considerable information for discernment of different sounds. An operational amplifier in a summing configuration combines the broadband and high-pass signals to produce a processed speech signal with enhanced intelligibility. Gain control circuitry associated with the high-pass channel reduces gain in the high-pass channel with increasing intensity of high-frequency speech signal components thereby tending to enhance the speech signal to an increasing degree at low signal levels and to otherwise produce a processed speech signal suitable for reproduction of natural-sounding speech.

High fidelity hearing aid amplifier

A single integrated circuit chip is provided with transistors, diodes, resistor and capacitors thereon for forming a variable gainamplifier (40) and gain control circuitry which provides a level dependent frequency response characteristic, operative at low signal levels to enhance gain at higher frequencies relative to that at lower frequencies. The gain control circuitry includes logarithmic rectifier means (48) operative to develop an AC output signal having a peak value varying as a logarithmic function of a signal level which may be that at the output of the variable gain amplifier (40). The AC output signal so developed is applied to a peak detector circuit in a compression ratio control circuit (46) to develop a DC signal which is amplified by a DC amplifier and applied to a control input of the variable gain amplifier (40).

Acoustic coupling of hearing aids to telephone receivers

Several significant problems are encountered by users of the telephone who wear a hearing aid and attempt to couple the aid acoustically to the telephone receiver. Many of the problems are caused by the inability of the aid wearer to achieve a good acoustic seal between the aid and the telephone receiver. This poor seal causes large losses at low frequencies and permits the intrusion of room noises onto the desired signal from the telephone receiver. Another problem, acoustic feedback between the aid receiver and microphone, is worsened by the resonance conditions present when the telephone handset is brought into proximity. These degradations have been characterized and a variety of solutions have been examined at Bell‐Northern Research. Low‐frequency response can be improved either in the aid or the handset. Attempts to reduce the perceived room noise level have been made using an adaptive noise cancellation technique. The feedback problem has been addressed via a variety of techniques, including use of an acoustic tube coupled to the aid microphone, automatic gain control circuitry, tracking notch filters, etc.

Thermal Noise Errors in DF Monopulse Systems Having Log Amplifiers

An analysis of the effects of thermal noise on the accuracy of direction finding (DF) monopulse systems which employ logarithmic amplifiers is presented. Numerical results are presented which indicate that a simple model may be used to compute rms thermal errors for a wide range of signal levels. Analytical results obtained in the limit of large signal-to-noise ratios are compared with standard results used to analyze monopulse systems employing automatic gain control (AGC) circuitry instead of log amplifiers.