High-gain Transimpedance Amplifier Research Articles

High-Resolution Drift Tube Ion Mobility Spectrometer with Ultra-Fast Polarity Switching.

Besides safety and security applications, ion mobility spectrometry (IMS) is increasingly used in other fields such as medicine, environmental monitoring and food quality analysis. However, some applications require gas chromatographic separation before analysis by IMS. Furthermore, different compounds in the sample may form positive or negative ions during ionization and therefore simultaneous detection of both ion polarities is highly beneficial to avoid two chromatographic runs of the same sample. This can be achieved by ultra-fast polarity switching of a single drift tube IMS, allowing for quasi-simultaneous detection of both ion polarities. By using a ramped aperture voltage during the switching process, we overcome the issue of excessive displacement currents at the detector during polarity switching, which usually lead to overdriving the output signal of the high-gain transimpedance amplifier. Furthermore, mechanical aperture grid oscillations caused by polarity switching were also reduced through the ramped aperture voltage. This enables a polarity switching time of only 7 ms at a drift voltage of 8 kV and a drift length of 103 mm, leading to a high resolving power of RP = 117. Requiring 50 ms to acquire a pair of positive and negative spectrum, the IMS achieves an acquisition rate of 20 Hz. It reaches limits of detection of 20 pptv for dimethyl methylphosphonate and 40 pptv for methyl salicylate. For demonstration, different hop varieties were investigated and could be clearly differentiated by considering both, the positive and negative spectra.

Simultaneous Ion Swarm Profiling and Ion Mobility Measurement using Ion Cameras.

When operated as a standalone analytical device, traditional drift tube ion mobility spectrometry (IMS) experiments require high-speed, high-gain transimpedance amplifiers to record ion separations with sufficient resolution. Recent developments in the fabrication of charge-sensitive cameras (e.g., IonCCD) have provided key insights for ion beam profiling in mass spectrometry and even served as detectors for miniature magnetic sector instruments. Unfortunately, these platforms have comparatively slow integration times (multiple ms), which largely precludes their use for recording ion mobility spectra, where sampling rates into the 10s of kHz are generally required. As a result, experiments that simultaneously probe the longitudinal and transverse mobility of an injected species using an array detector have not been reported. To address this duty-cycle mismatch, a frequency encoding strategy is used to evaluate ion swarm characteristics, while directly capturing ion mobility information using the Fourier transform. This apparatus described allows the ion beam to be profiled over the full course of the experiment and establishes the foundation to examine axial and longitudinal drift velocities simultaneously.

Differential high gain transimpedance amplifier with –3dB-bandwidth extension

In this article, a three-stage transimpedance amplifier (TIA) is designed and optimized to convert the input current to the output voltage and amplify it. The amplifier consists of a single-to-differential cross-coupled modified RGC (Regulated Cascode) input stage. The proposed TIA adopts a gm-boosted technique in the input stage by adding an auxiliary circuit that increases the –3dB-bandwidth by about 580 MHz, which lowers the input impedance resulting in a high input pole frequency. Also, an fT doubler stage and a third stage with minimum power consumption for fT doubling (second stage) and increasing gain are used respectively. The area consumption is reduced by replacing the conventional fT doubler topology resistors with transistors. Both stages of designed amplifiers have a variable gain mechanism. In the post-layout simulation, the circuit has a variable gain mechanism and a gain of up to 99 dBΩ with a –3dB-bandwidth of 720 MHz and an input-referred noise of 11.42 PA/√Hz. The post layout simulation is performed in 180 nm CMOS technology. The circuit's core power consumption is 6.0624 mW and occupies 0.051 mm × 0.06136 mm of area.

Design of a Current Sensing System with TIA Gain of 160 dBΩ and Input-Referred Noise of 1.8 pArms for Biosensor.

This paper proposes a high-gain low-noise current signal detection system for biosensors. When the biomaterial is attached to the biosensor, the current flowing through the bias voltage is changed so that the biomaterial can be sensed. A resistive feedback transimpedance amplifier (TIA) is used for the biosensor requiring a bias voltage. Current changes in the biosensor can be checked by plotting the current value of the biosensor in real time on the self-made graphical user interface (GUI). Even if the bias voltage changes, the input voltage of the analog to digital converter (ADC) does not change, so it is designed to plot the current of the biosensor accurately and stably. In particular, for multi-biosensors with an array structure, a method of automatically calibrating the current between biosensors by controlling the gate bias voltage of the biosensors is proposed. Input-referred noise is reduced using a high-gain TIA and chopper technique. The proposed circuit achieves 1.8 pArms input-referred noise with a gain of 160 dBΩ and is implemented in a TSMC 130 nm CMOS process. The chip area is 2.3 mm2, and the power consumption of the current sensing system is 12 mW.

High Gain, Low Noise and Power Transimpedance Amplifier Based on Second Generation Voltage Conveyor in 65 nm CMOS Technology.

A transimpedance amplifier (TIA) based on a voltage conveyor structure designed for high gain, low noise, low distortion, and low power consumption is presented in this work. Following a second-generation voltage conveyor topology, the current and voltage blocks are a regulated cascode amplifier and a down converter buffer, respectively. The proposed voltage buffer is designed for low distortion and low power consumption, whereas the regulated cascode is designed for low noise and high gain. The resulting TIA was fabricated in 65 nm CMOS technology for logic and mixed-mode designs, using low-threshold voltage transistors and a supply voltage of ±1.2 V. It exhibited a 52 dBΩ transimpedance gain and a 1.1 GHz bandwidth, consuming 55.3 mW using a ±1.2 V supply. Our preamplifier stage, based on a regulated cascode, was designed considering detector capacitance, bonding wire, and packaging capacitance. The voltage buffer was designed for low-power consumption and low distortion. The measured input-referred noise of the TIA was 22 pA/√Hz. The obtained total harmonic distortion of the TIA was close to 5%. In addition, the group delay is constant for the considered bandwidth. Comparisons against published results in terms of area (A), power consumption (P), bandwidth (BW), transimpedance gain (G), and noise (N) are were performed. Both figures of merit FoMs—the ratio √ (G × BW) and P × A—and FoM/N values demostrated the advantages of the proposed approach.

How to maximize the bandwidth without increasing the noise in op-amp-based transimpedance amplifiers using positive feedback.

The bandwidth of very high gain (≥100 MV/A) transimpedance amplifiers is restricted to below 100 kHz, unless measures are employed to mitigate the effect of circuit parasitic capacitances. Current approaches involve significantly increased circuit complexity and component count. They may suffer unwanted noise pickup or destructive capacitive coupling to ground, the latter restricting the available bandwidth. We demonstrate that combining a positive feedback circuit with a low-pass filter network extends the bandwidth of a transimpedance amplifier out to the limit of gain peaking (>1 MHz) without increasing the noise signal. The circuit uses a single inverting amplifier and very large feedback-resistance to provide a canceling parasitic-capacitance positive feedback signal. This can negate both the negative feedback-resistor parasitic-capacitance and the input/output pin parasitic-capacitance of the transimpedance amplifier. The circuit solves the problem of destructive distributed-capacitive coupling to ground along the feedback resistor.

A Novel Inductorless Design Technique for Linear Equalization in Optical Receivers

To mitigate the trade-off between gain and bandwidth of CMOS multistage amplifiers, a receiver front-end (FE) that employs a high-gain narrowband transimpedance amplifier (TIA) followed by an equalizing main amplifier (EMA) is proposed. The EMA provides a high-frequency peaking to extend the FE’s bandwidth from 25% to 60% of the targeted data rate fbit. The peaking is realized by adding a pole in the feedback paths of an active feedback-based wideband amplifier. By embedding the peaking in the main amplifier (MA), the front-end meets the sensitivity and gain of conventional equalizer-based receivers with better energy efficiency by eliminating the equalizer stages. Simulated in TSMC 65 nm CMOS technology, the proposed front-end achieves 7.4 dB and 6 dB higher gain at 10 Gb/s and 20 Gb/s, respectively, compared to a conventional front-end that is designed for equal bandwidth and dissipates the same power. The higher gain demonstrates the capability of the proposed technique in breaking the gain-bandwidth trade-off. The higher gain also reduces the power penalty incurred by the decision circuit and improves the sensitivity by 1.5 dB and 2.24 dB at 10 Gb/s and 20 Gb/s, respectively. Simulations also confirm that the proposed FE exhibits a robust performance against process and temperature variations and can support large input currents.

High Spatial Resolution Optical Fiber Two Color Pyrometer With Fast Response

Among the different temperature measurement techniques providing micrometer resolution none of them provide fast response and easy access to close distances to the target surface in difficult to access areas. Optical fiber pyrometers provide that access but previous works used large optical fibers with numerical apertures limiting the minimum spot size to be measured. In this study, we propose a novel two colour optical fiber pyrometer based on a low diameter and numerical aperture optical fiber, low-noise photodetectors and high-gain transimpedance amplifiers with a high spatial resolution in the micrometre range and fast response. Using standard optical fibers and related devices provides also a low-cost system. The developed pyrometer presents a high spatial resolution of 16 μm for a target surface at 25 μm with a wide temperature range of 300 to 1200°C it being the highest spatial resolution for this kind of temperature systems. Theoretical analysis and measurements for different pyrometer configurations are reported. This study will help further the microthermography applications in machining processes.

A Sub-mW 18-MHz MEMS Oscillator Based on a 98-dBΩ Adjustable Bandwidth Transimpedance Amplifier and a Lamé-Mode Resonator.

This paper presents a microelectromechanical system (MEMS)-based oscillator based on a Lamé-mode capacitive micromachined resonator and a fully differential high-gain transimpedance amplifier (TIA). The proposed TIA is designed using TSMC 65 nm CMOS technology and consumes only 0.9 mA from a 1-V supply. The measured mid-band transimpedance gain is 98 dB and the TIA features an adjustable bandwidth with a maximum bandwidth of 142 MHz for a parasitic capacitance of 4 pF. The measured input-referred current noise of the TIA at mid-band is below 15 pA/. The TIA is connected to a Lamé-mode resonator, and the oscillator performance in terms of phase noise and frequency stability is presented. The measured phase noise under vacuum is −120 dBc/Hz at a 1-kHz offset, while the phase noise floor reaches −127 dBc/Hz. The measured short-term stability of the MEMS-based oscillator is ±0.25 ppm.

10 Gb/s inductorless single-stage high-gain transimpedance amplifier for optical communication receiver

In the present paper, by simultaneous use of shunt feedback with regulated Cascode structures, a new transimpedance amplifier was presented, which increases the transimpedance limit. This amplifier is very low-noise due to its pseudo-differential nature and partial noise cancellation. The simultaneous use of these two structures led to a reduction in the components of the circuit, power consumption, noise, and the chip area. Moreover, the circuit’s differential output eliminated the need for a separate stage for the single-ended to differential signal converter. The inductorless TIA was simulated with TSMC 0.18 μm RF CMOS technology, with a 3-dB bandwidth equal to 7.38 GHz, proper for functioning at 10 Gb/s, with a 250 fF capacitor to apply the effect of photodiode capacitance at the input. Besides, the single-stage transimpedance gain of 59.7 dBΩ is yielded. Furthermore, the power consumption from 1.8 V voltage source and input-referred current noise were calculated as 5 mW and 12.2 pA/√Hz, respectively.

Fiber-Optic Pyrometer with Optically Powered Switch for Temperature Measurements.

We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also report a shutter based on an optical fiber switch which is optically powered to provide a reference signal in an optical fiber pyrometer measuring from 200 to 550 °C. The tests show the potential of remotely powering via optical means a 300 mW power-hungry optical switch at a distance of 100 m, avoiding any electromagnetic interference close to the measuring point.

High-Gain Transimpedance Amplifier for Flexible Radiation Dosimetry Using InGaZnO TFTs

This paper presents a novel high-gain transimpedance amplifier for flexible radiation sensing systems that can be used as large-area dosimeters. The circuit is implemented with indium-gallium-zinc-oxide thin-film-transistors and uses two stages for the amplification of the sensor signal (current). The first stage consists of cascode current mirrors with a diode connected load that performs current amplification and voltage conversion. Then, the first stage is followed by a voltage amplifier based on a positive feedback topology for gain enhancement. The proposed circuit converts nano-ampere (10 nA) currents into hundreds of millivolts (280 mV), showing a gain around 149 dB and a power consumption of 0.45 mW. The sensed radiation dose level, in voltage terms, can drive the next stages in the radiation sensing system, such as analog to digital converters. These radiation sensing devices can find potential applications in real-time, large area, flexible health, and security systems.

A MATLAB-Based Method for Designing High-Gain Resonant Transimpedance Amplifiers

In this paper, we propose a novel efficient method for the design of high-gain resonant transimpedance amplifiers (TIAs) using MATLAB. The procedure provides the designer with an effective tool, useful to explore the effects of different device parameter combinations in complex network topologies used in several application fields. We applied this method to improve the detection capability of a previously designed chlorophyll-A (Chl-A) sensor, in order to in-vivo assess the seawater quality. By exploiting the interesting bandpass behavior exhibited by a T feedback network, we were able to redesign the resonant TIA stage of a low-cost lock-in amplifier working at 1 kHz, easily increasing the gain by a factor of 100, and reaching an overall gain of 216 dB while reducing the detectivity to almost 500 fA. Moreover, the proposed analysis provides the optimal circuit parameter values for a wide working frequency range without further numerical optimization, giving an interesting perspective of its potential use in those telecommunication applications where high sensitivity is required.

Performances of a HGCDTE APD Based Detector with Electric Cooling for 2-μmDIAL/IPDA Applications

1. ABSTRACT In this work we report on design and testing of an HgCdTe Avalanche Photodiode (APD) detector assembly for lidar applications in the Short Wavelength Infrared Region (SWIR : 1,5 - 2 µm). This detector consists in a set of diodes set in parallel -making a 200 µm large sensitive area- and connected to a custom high gain TransImpedance Amplifier (TIA). A commercial four stages Peltier cooler is used to reach an operating temperature of 185K. Crucial performances for lidar use are investigated : linearity, dynamic range, spatial homogeneity, noise and resistance to intense illumination.

Design of low-noise transimpedance amplifiers with capacitive feedback

This paper reports on a new topology and design methodology for ultra-low noise and high-gain transimpedance amplifiers. This paper also reports on measurement results of two implemented ICs based on the proposed topology and fabricated in 130 nm IBM and 180 nm TSMC technologies. A capacitive feedback topology is implemented as a noise-efficient feedback network, analytical noise calculations in this family of TIA circuits are presented, and optimum noise criterion is derived. The saturation and instability problem of TIA circuits resulted from DC dark current of the input photodiodes is also addressed and a simple yet efficient feedback solution is proposed. The measurement results of 130 nm chip show average input referred noise of 2.67 pA/?Hz with bandwidth of 81 kHz to 1.76 GHz and transimpedance gain of 76 dB? while dissipating 13.7 mW from a 1.5 V power supply, including the output buffer. The measurement results of 180 nm chip show average input referred noise of 3.18 pA/?Hz with bandwidth of 72 kHz to 1.62 GHz and transimpedance gain of 75 dB? while dissipating 26.3 mW from a 2.2 V power supply, including the output buffer.

In-circuit-measurement of parasitic elements in high gain high bandwidth low noise transimpedance amplifiers.

Parasitic elements play an important role in the development of every high performance circuit. In the case of high gain, high bandwidth transimpedance amplifiers, the most important parasitic elements are parasitic capacitances at the input and in the feedback path, which significantly influence the stability, the frequency response, and the noise of the amplifier. As these parasitic capacitances range from a few picofarads down to only a few femtofarads, it is nearly impossible to measure them accurately using traditional LCR meters. Unfortunately, they also cannot be easily determined from the transfer function of the transimpedance amplifier, as it contains several overlapping effects and its measurement is only possible when the circuit is already stable. Therefore, we developed an in-circuit measurement method utilizing minimal modifications to the input stage in order to measure its parasitic capacitances directly and with unconditional stability. Furthermore, using the data acquired with this measurement technique, we both proposed a model for the complicated frequency response of high value thick film resistors as they are used in high gain transimpedance amplifiers and optimized our transimpedance amplifier design.

Design of a novel MEMS resonator based neuromorphic oscillator

A novel MEMS based neuromorphic oscillator is presented. Due to compatibility with CMOS process, on-chip integration of electro-statically actuated microresonators is possible with very small size. Also, taking advantage of sacrificial sidewall spacer technique for fabrication of 100nm vertical gap, as low actuation voltages as 0.5V is enough for such resonators. Oscillatory neuron dynamics are also studied and design of the resonator and its characteristics are described as a neuromorphic oscillator. There are several practical barriers associated with MEMS implementation of neuromorphic oscillators such as existence of near-to-main mode spurious modes, requiring of UHF high gain trans-impedance amplifier because of very high motional resistance of such resonators, and automatic amplitude control circuit which all investigated in the paper and surmounted as well. A coupling technique for weak connection of such resonators is also described in the paper which allows mechanical low velocity connection of UHF contour mode disk resonators for the first time.

Low-Noise, High-Gain Transimpedance Amplifier Integrated With SiAPD for Low-Intensity Near-Infrared Light Detection

A fully integrated near-infrared spectroscopy photoreceiver including two new silicon avalanche photodiodes (SiAPDs) and a new transimpedance amplifier (TIA) is proposed in this paper. SiAPDs are designed in p+/n-well structure with guard-rings realized in different shapes. The TIA front-end has been designed using distributed-gain concept combined with resistive-feedback and common-gate topology to reach low-noise, low-power consumption, high gain-bandwidth product characteristics and it is robust against power-supply variation (1-3 V). This circuit is developed using 0.35 μm CMOS technology and the measurement results are compared with other results from the literature. The designed rectangular and octagonal SiAPDs have the avalanche gain of 100 and 45 with the breakdown voltage of 9 and 6 V and the photon absorption efficiency of 45% and 25% at 800 nm. Fabricated TIA offers high-transimpedance gain (up to 250 MV/A), tunable BW (1 kHz-1 GHz), extremely low input and output noises (100 fA/√Hz, 1.8 μV/√Hz), and low-power consumption (0.8 mW). The impact and effects of on-chip integration of SiAPD and TIA front-end have been also measured and evaluated.

A high dynamic range pulse counting detection system for mass spectrometry

A high dynamic range pulse counting system has been developed that demonstrates an ability to operate at up to 2e8 counts per second (cps) on a triple quadrupole mass spectrometer. Previous pulse counting detection systems have typically been limited to about 1e7 cps at the upper end of the systems dynamic range. Modifications to the detection electronics and dead time correction algorithm are described in this paper. A high gain transimpedance amplifier is employed that allows a multi-channel electron multiplier to be operated at a significantly lower bias potential than in previous pulse counting systems. The system utilises a high-energy conversion dynode, a multi-channel electron multiplier, a high gain transimpedance amplifier, non-paralysing detection electronics and a modified dead time correction algorithm. Modification of the dead time correction algorithm is necessary due to a characteristic of the pulse counting electronics. A pulse counting detection system with the capability to count at ion arrival rates of up to 2e8 cps is described. This is shown to provide a linear dynamic range of nearly five orders of magnitude for a sample of aprazolam with concentrations ranging from 0.0006970 ng/mL to 3333 ng/mL while monitoring the m/z 309.1 → m/z 205.2 transition. This represents an upward extension of the detector's linear dynamic range of about two orders of magnitude. A new high dynamic range pulse counting system has been developed demonstrating the ability to operate at up to 2e8 cps on a triple quadrupole mass spectrometer. This provides an upward extension of the detector's linear dynamic range by about two orders of magnitude over previous pulse counting systems.

Design of RF MEMS Based Oscillatory Neural Network for Ultra High Speed Associative Memories

Microelectromechanical systems are utilized alongside with transistor amplifiers and resistive connections for implementing of oscillatory associative memories. Phase locking is studied in such a network and all requirements of the circuit level implementation are satisfied. A very high gain trans-impedance amplifier operating in 1 GHz in addition to a novel automatic amplitude control circuit is employed to remove amplitude dynamics of the system. Requiring resonator characteristics are extracted and calculated as well. A new method for initialization of the network is proposed. Each neuron consumes 1.08 mW from a 1.8 V power supply. The convergence time of a typical network trained by Hebbian rule is less than 1.5 ns which results in an ultra high speed analog signal processing system.