Input Low Noise Research Articles

The MEMSamp: using (RF-)MEMS switches for the micromechanical amplification of electronic signals

Semiconductor-based electronic amplifiers are ubiquitous in the modern world, but have fundamental limitations, such as the impossibility of using them at extreme temperatures and their sensitivity to ionizing radiation. Also, they inherently have various sources of electronic noise. We have developed a MEMS (micro-electromechanical systems) switch based amplifier in which an electronic signal is mechanically amplified in power: the MEMSamp. The new device is suitable for the same applications as semiconductor-based amplifiers, with the additional advantage of a purely mechanical operation, circumventing the limitations mentioned above. A thermal noise analysis shows that a MEMSamp may be operated with much lower input noise than state-of-the-art semiconductor amplifiers. We expect optimized amplifiers based on this principle to be applicable in fields ranging from low-noise preamplifiers to radiation-hard power amplifiers, and from ultra-high temperature electronics to spacecrafts.

Design and characterization of a multi-channel front-end readout ASIC with low noise and large dynamic input range for APD-based PET imaging

This paper represents the design of a low-noise, wide band multi-channel readout integrated circuit (IC) used as front-end readout electronics of Avalanche Photo Diodes (APD) dedicated to a small animal Positron Emission Tomography (PET) system. The first 10-channel prototype chip (APD_Chip) of the analog parts has been designed and fabricated in a 0.35-μm CMOS process. Every channel of the APD_Chip includes a charge-sensitive preamplifier (CSA), a CR-(RC)2 shaper, and an analog buffer. In each channel, the CSA reads charge signals (10 bits dynamic range) from an APD array having 10 pF of capacitance per pixel. A linearized degenerated differential pair which ensures high linearity in all dynamical range is used as the high feedback resistor for preventing pile up of signals. The designed CSA has the capability of compensating automatically up to 200 nA leakage current from the detector. The CR-(RC)2 shaper filters and shapes the output signal of the CSA. An equivalent input noise charge obtained from test is 275 e? + 10 e?/pF. In this paper the prototype is presented for both its circuits design and its test results.

Design of a Multi-Channel Front-End Readout ASIC With Low Noise and Large Dynamic Input Range for APD-Based PET Imaging

This paper represents the design of a low-noise, wide band multi-channel readout integrated circuit (IC) used as front end readout electronics of avalanche photo diodes (APD) dedicated to a small animal positron emission tomography (PET) system. The first ten-channel prototype chip (APD-Chip) of the analog parts has been designed and fabricated in a 0.35 μm CMOS process. Every channel of the APD_Chip includes a charge-sensitive preamplifier (CSA), a CR-(RC)2 shaper, and an analog buffer. In a channel, the CSA reads charge signals (10 bits dynamic range) from an APD array having 10 pF of capacitance per pixel. A linearized degenerated differential pair which ensures high linearity in all dynamical range is used as the high feedback resistor for preventing pile up of signals. The designed CSA has the capability of compensating automatically up to 200 nA leakage current from the detector. The CR-(RC)2 shaper filters and shapes the output signal of the CSA. An equivalent input noise charge obtained from test is 275 e -+ 10 e-/pF. In this paper the prototype is presented for both its theoretical analysis and its test results.

Design of a reconfigurable gain low noise amplifier for multistandard receivers in 65 nm technology

This paper presents a broadband variable gain low noise amplifier (LNA) suitable for multistandard receivers. The LNA has been implemented in 65 nm CMOS technology. To provide low noise input impedance matching, a negative-shunt feedback matching has been proposed. This LNA achieves a simulated noise figure less than 1.94 dBm at the highest gain (25 dB) over a wideband frequency (100 MHz–1 GHZ). Furthermore, the gain of the LNA is variable over a wide range of 11 dB and S11 is less than −19 dB over the entire desired frequency band. The −3 dB bandwidth is 2 GHz, the IIP3 is −6.5 dBm at the highest gain. The LNA drains 18.3 mA from a 1.2 V supply and 7.3 mA from a 2.2 V supply. In addition, a single-ended to differential converter (SDC) is presented providing a differential output for the LNA and increasing the gain re-configurability range to 20 dB.

Development of X-ray CCD camera system with high readout rate using ASIC

We report on the development of an X-ray charge-coupled device (CCD) camera system with high readout rate using application-specific integrated circuit (ASIC) and Camera Link standard. The distinctive Δ Σ type analog-to-digital converter is introduced into the chip to achieve effective noise shaping and to obtain a high resolution with relatively simple circuits. The unit test proved moderately low equivalent input noise of 70 μ V with a high readout pixel rate of 625 kHz, while the entire chip consumes only 100 mW. The Camera Link standard was applied for the connectivity between the camera system and frame grabbers. In the initial test of the whole system, we adopted a P-channel CCD with a thick depletion layer developed for X-ray CCD camera onboard the next Japanese X-ray astronomical satellite. The characteristic X-rays from 109Cd were successfully read out resulting in the energy resolution of 379 ( ± 7 ) eV (FWHM) @22.1 keV, that is, Δ E / E = 1.7 % with a readout rate of 44 kHz.

Capacitive-Sensor Interface With High Accuracy and Stability

This paper presents a capacitive-sensor interface with high accuracy and excellent stability. The range of the measured capacitance is up to 1 pF. The implemented circuit tolerates cable capacitances of up to 1 nF. Depending on the operation mode, the conversion time varies between 39 and 100 mus. The measurement principle permits a mode with compensation of small sensor leakage currents. The reference units are frequency, resistance, and resistance ratios, which provide high initial accuracy and a long-term stability. The measured temperature coefficient of the capacitance converter is about 2 ppm/K. A special multislope analog-to-digital conversion (ADC) is used, which, to increase the resolution, transfers itself at the beginning and at the end of the conversion process into an oversampling conversion. Based on the band-pass filtering function of the implemented ADC technique and the low-noise input stage used, a dynamic range of better than 14 b has been achieved for a cable capacitance that is less than 400 pF.

Low-voltage low-power integrated analog lock-in amplifier for gas sensor applications

We propose a low-voltage (±1 V) low-power (3 mW) lock-in amplifier, fabricated in a standard CMOS technology (AMS 0.35 μm) with analog features and utilized for low-frequency gas sensor applications. The proposed lock-in architecture, which works at a fixed input signal frequency (77 Hz) with a very low input noise (only 34 nV/(sqrt(Hz)) @ 77 Hz), can be utilized to detect very small quantities of reagent gas, especially if combined with other techniques, as the sensor thermal modulation. The integrated solution has been fabricated on a single chip, requiring a reduced silicon area (about 5 mm 2). Experimental measurements have confirmed the capability of the proposed lock-in system to reveal very small signals, in particular, testing the whole system for gas detection, a resolution improvement by a factor valued about 50 allows to detect gas concentrations lower than 1 ppm.

Current-Mode High-Accuracy High-Precision CMOS Amplifiers

In low-voltage, deep sub- mum analog CMOS circuits, the accuracy and precision can be limited by the finite gain as well as by the input offset and 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise voltages of opamps. Here, we show how to design high-accuracy high-precision CMOS amplifiers by properly applying dynamic element matching to a second-generation current conveyor (CCII); if all of the critical, nominally identical transistor pairs are dynamically matched, the resulting amplifier has low residual input offset and noise voltages. When compared with chopper or traditional dynamic element-matching amplifiers, the proposed approach alleviates the tradeoff between output swing and output resistance and is more robust against the finite opamp gain. Transistor-level simulations confirm theoretical results.

IIP2 Calibration by Injecting DC Offset at the Mixer in a Wireless Receiver

A major contributor to degraded input-referred second-order intercept point (IIP2) in integrated RF systems-on-chips is local oscillator (LO) leakage to the input of RF circuits. In this brief, we present a digital calibration technique for improving IIP2 by injecting controlled dc offset at the mixer output through a three-port network of switched-capacitor filters. The dc offset at mixer output gets up-converted to LO frequency at the input of RF circuits due to poor reverse isolation of the receiver front-end. By controlling the amplitude of the injected dc, IIP2 degradation due to LO leakage at the input of RF amplifiers can be compensated. Mathematical analysis is presented and supported by measurement data from a quad-band GSM/GPRS receiver implemented in 90-nm digital CMOS process. Calibrated IIP2 of 50 dBm is reported for the receiver at low-noise amplifier input.

Relative Intensity Noise Performance of Wavelength Converters Based on Four-Wave Mixing in Semiconductor Optical Amplifiers

We present a numerical and experimental study of the relative intensity noise (RIN) induced by the four-wave mixing (FWM) based wavelength conversion process in a semiconductor optical amplifier (SOA). The study is based on the RIN evaluation of the converted signal, under various operating conditions (input power levels and wavelength detuning) and input noise characteristics. A detailed numerical model is employed to simulate the FWM process, taking into account the amplified spontaneous emission (ASE) noise, the wavelength dependent gain, and the interaction of four waves in the SOA (two input waves and two product waves). It is shown that for low noise input signals, the output RIN is determined by the power levels of the pump and signal and the wavelength detuning. Operation under saturation allows reduction of the output RIN levels with respect to the input

Low capacitance, low kickback noise input stage of a multi-level quantizer with dithering and multi-threshold generation for a multi-bit sigma-delta modulator

An N-level quantizer circuit (14) has an analog input terminal and N-1 digital output terminals, and includes a sampling circuit (SW samp) coupled to the input terminal for providing a sampled input voltage signal; at least one preamplifier stage (14A) for converting the sampled input voltage signal to a current signal and providing an amplified sampled input signal; and N-1 comparator stages (14B) each having an input coupled to an output of the at least one preamplifier stage (14A) and sharing the input current equally. Individual ones of the N-1 comparator stages (14B) operate to compare the amplified sampled signal to an associated one of N-1 reference signals. The quantizer (14) further includes N-1 latches (14C), individual ones of which latch an output state of one of the N-1 comparators and have an output coupled to one of the N-1 digital output terminals of the quantizer circuit (14).

An InGaAs-InP HBT differential transimpedance amplifier with 47-GHz bandwidth

Return-to-zero differential phase-shift keying applications require a differential amplifier with high bandwidth, high gain, low noise, and good input impedance match. In this paper, we describe an InGaAs-InP heterostructure bipolar transistor differential transimpedance amplifier with high bandwidth of 47 GHz and high gain of 56 dB-/spl Omega/. The input-referred current noise is less than 35 pA//spl radic/Hz over the measurement range up to 40 GHz.

Five-Millimeter Radiometric Receiver with A Low-Noise Input Amplifier

We consider the structure of a small-size superheterodyne modulation-type radiometric receiver with a low-noise transistor amplifier (LNTA) at the input. With LNTA noise coefficient 3.5 dB, the fluctuation sensitivity of the radiometric receiving unit was 0.025 K in the input-frequency range 56-60 GHz for a time constant 1 s.

Synthesis of Basic Components of a Low-Noise Input Circuit for Millimeter Wavelengths;

Synthesis of Basic Components of a Low-Noise Input Circuit for Millimeter Wavelengths;

Design of narrow-band photoreceivers by means of the photodiode intrinsic conductance

The photodiode intrinsic conductance is a versatile parameter for designing photoreceivers used in lightwave-microwave systems. A short review is given on how the transimpedance and equivalent input noise current of an optical receiver can be calculated. The design of monolithically integrated narrow-band photoreceivers for microwave-via-fiber applications at 10 GHz is demonstrated. The photoreceivers were fabricated using GaAs-based pseudomorphic high electron-mobility transistor monolithically integrated with metamorphic InGaAs photodiodes. For such a photoreceiver, a very low equivalent input noise current of 5.7 pA per square-root hertz and a high optoelectronic conversion gain of 64.1 dBV/W were measured in good agreement with simulations.

An auto-gain control transimpedance amplifier with low noise and wide input dynamic range for 10-Gb/s optical communication systems

This paper describes a 10-Gb/s transimpedance amplifier (TIA), fabricated in a 0.1-/spl mu/m-p-HEMT technology. To improve the optical overload characteristics, an automatic gain control (AGC) circuit is included. The measured results show excellent performance, transimpedance of 63.3 dB/spl Omega/ (1.46 k/spl Omega/), bandwidth of 8.0 GHz, and equivalent input noise current density of 6.5 pA/rtHz. When the bit error rate is 10/sup -9/, the minimum sensitivity and the optical overload are -21.2 dBm, +4.3 dBm, respectively, using a 0.8 A/W pin photodiode (PD). The power dissipation is about 0.5 W from a single -5-V supply. The die area is 1.3/spl times/1.6 mm/sup 2/.

A fast preamplifier for proximity focused HPDs

Abstract The proximity focused hybrid photo diode (HPD), a new type of light detector insensitive to uniform magnetic fields, will be employed in the inner region of the FINUDA detector coupled to a simple, cheap, low noise and low input impedance fast preamplifier (PA): the design and the performances are presented and discussed.

Low-Noise Amperometric Detector for Use in Capillary Electrophoresis

A low noise amperometric detector suitable for capillary electrophoresis has been constructed from integrated operational amplifiers with low noise and low input bias current. It includes a potentiostat and a vertical wall-jet detection cell. The circuit design of the potentiostat, the construction of the detection cells, and methods for minimizing the noise are described. Performance tests of the detector were performed for the determination of catecholmines.

Design and realization of an optimal current sensitive CCC

The sensitivity of an overlapped tube cryogenic current comparator (CCC), coupled to a SQUID by means of a flux transformer, is calculated and compared with measurements. Conditions for optimal coupling between the CCC and the SQUID are derived. Based on these, an optimal CCC for precision measurements of very small currents in the nanoampere range has been designed. The paper describes the construction and testing of some parts of the system. An essential element is a home-made dc SQUID with low current noise and low inductance input coil equal to that of the CCC overlapped shield, which we use as sensing coil.

Versatile millimeter-wave interferometer with two frequencies in the divertor region of JT-60U

A millimeter-wave interferometer having a capability of concomitant electron temperature measurement, based on the electron cyclotron absorption (ECA) technique, has been developed for divertor diagnostics in JT-60U. Three lines of sight, which pass through the X point horizontally, the inboard divertor and the outboard divertor, are chosen. Two transmitter/receiver units with frequencies of 217 and 183 GHz are employed in order to eliminate the spurious vibration effect using a two color scheme. The two independent units are also arranged to enable two sight line measurements without the vibration compensation. Furthermore, these units allow us to apply the simultaneous ECA diagnostic. Due to the complexity of the transmission line inside the tokamak, the insertion loss is as large as 65 dB. However, the interferometer system can be operated with the signal-to-noise (S/N) ratio of about 20 dB due to the low equivalent input noise of −90 dB m. The measurements performed for several types of the JT-60U discharges indicate the feasibility of the system and the rapid reduction of the electron density near the X point at the high confinement mode transition is first demonstrated.