Input Noise Current Spectral Density Research Articles

Ultra-low-noise transimpedance amplifier in cryogenic STM for studying novel quantum states by measuring shot noise

An ultra-low-noise large-bandwidth transimpedance amplifier (TIA) for cryogenic scanning tunneling microscope (CryoSTM) is proposed. The TIA connected with the tip-sample component in CryoSTM is called as CryoSTM-TIA. Its transimpedance gain is as high as 1 GΩ, and its bandwidth is over 300 kHz, but its equivalent input noise current power spectral density is less than 4 (fA)2/Hz at 100 kHz. The low inherent noise for the CryoSTM-TIA is due to its special design: (1) its pre-amplifier is made of a pair of low-noise cryogenic high electron mobility transistors (HEMTs); (2) the noise generated by one HEMT is eliminated by a large capacitor; (3) the capacitance of the cable connected the gate of the other HEMT to the tip is minimized; (4) thermal noise sources, such as the feedback resistor, are placed in the cryogenic zone. The dc output voltage drift of the CryoSTM-TIA is very low, as 5 μV/°C. The apparatus can be used for measuring the scanning tunneling differential conductance spectra, especially the scanning tunneling shot noise spectra (STSNS) of quantum systems, even if the shot noise is very low. It provides a universal tool to study various novel quantum states by measuring STSNS, such as detecting the Majorana bound states.

A CMOS transimpedance amplifier with broad-band and high gain based on negative Miller capacitance

A CMOS transimpedance amplifier (TIA) with broad band and high gain based on negative Miller capacitance and capacitive degeneration has been proposed and designed. The theoretical analysis shows that by introducing negative Miller capacitance into the feedforward common gate (FCG) amplifier circuit, the bandwidth limitation caused by the internal parasitic capacitance can be reduced, and by cascading the capacitive degeneration-based common source (CS) amplifier as the gain stage, the amplifier gain can be improved simultaneously. The proposed TIA is designed and simulated in TSMC 65 nm CMOS process, The simulation results show that the −3 dB bandwidth of the amplifier circuit is 23.7 GHz, the transimpedance gain is 60.1 dBΩ, the average equivalent input noise current spectral density is less than 40.7 pA/√Hz, the power consumption is 4.8 mW, and the circuit layout area is 0.0027 mm2. In Comparison to the published TIA circuits, the bandwidth of the designed CMOS TIA is increased by 12.7 GHz, the gain is increased by 18.1 dBΩ and the circuit layout area becomes smaller. All the results demonstrate that the designed TIA can be used in the photoelectric detection circuit with broader bandwidth and higher gain.

Low-noise large-bandwidth transimpedance amplifier for measuring scanning tunneling shot noise spectra in cryogenic STM and its applications

Shot noise is a powerful tool to study quantum systems. In this work, a design of transimpedance amplifier (TIA) for a cryogenic scanning tunneling microscope (CryoSTM) is proposed to meet the requirements of the shot noise measurements for quantum systems. In the TIA, the preamplifier is made of the low-noise low-power cryogenic high electron mobility transistors. With the high transimpedance gain of 1 GΩ, the bandwidth of the proposed TIA is larger than 300 kHz. In the CryoSTM, the TIA with the tip-sample component is called as CryoSTM-TIA. The bandwidth of the proposed CryoSTM-TIA is still larger than 300 kHz. Its equivalent input noise current power spectral density is less than 30(fA)2/Hz at 100 kHz. It is detailed, for quantum systems, by using the CryoSTM-TIA, how to measure scanning tunneling current spectra, scanning tunneling differential conductance spectra, and scanning tunneling noise current power spectra, in atomic scale, and then extract their scanning tunneling shot noise spectra. Thus, it is possible to study novel quantum phenomena in various quantum systems by measuring shot noise with the CryoSTM-TIA, such as the Andreev reflection in atomic scale, the Kondo effect in a single molecular magnet, and the existence of Majorana bound states, etc.

Wideband inductorless transimpedance amplifier using capacitive degeneration and negative capacitance

AbstractThis paper presents a new wideband inductorless CMOS transimpedance amplifier (TIA) for 10Gb/s applications. In this proposed TIA, inverter‐based common‐drain active feedback topology is modified by introducing a cascode transistor to reduce input impedance. Furthermore, capacitive degeneration and negative capacitance techniques are employed by using a single capacitor. Both techniques extend the bandwidth. Mathematical analysis of the proposed TIA has been done using the small signal model to describe bandwidth extension. To verify the theoretical description, the proposed TIA is simulated using TSMC 0.18 μm CMOS technology at 1.8 V power supply with 4.3 mW power consumption. The input photodiode capacitance is 0.25 pF. Simulation results show the transimpedance gain of 51.4 dBΩ and 7.6 GHz bandwidth. The input noise current spectral density is 27 pA/√Hz.

A Multi-Channel Low-Noise Analog Front End Circuit for Linear LADAR

In this brief, a 32-channel analog front end circuit featured with high gain, high bandwidth, and low noise characteristics is designed. The proposed three-stage analog front end (TS-AFE) includes a variable gain transimpedance amplifier, a differential voltage amplifier, and an analog equalizer. The first stage adopts the shunt-feedback topology to optimize the overall noise, the second stage helps to enlarge the input dynamic range further, and the last stage boosts the channel bandwidth. Furthermore, a 6-bit current digital-to-analog converter (DAC) is integrated in the equalizer to produce a built-in threshold voltage. The 32-channel TS-AFE chip is fabricated with 0.18-μm CMOS technology. The measurement results show that with the highest gain configuration, the circuit realizes 101.6 dB transimpedance gain, 190 MHz bandwidth, and 2.6 pA/sqrt(Hz) input noise current spectral density, respectively. The minimum detectable current achieves 0.4 μA with SNR = 10. The maximum output voltage swing is greater than 1000 mV, and the linear dynamic range reaches 64 dB. The power consumption per channel is as low as 37 mW from a single 3.3 V supply.

High-Gm differential regulated cascode transimpedance amplifier

A differential cross-coupled regulated cascode(RGC)transimpedance amplifier(TIA)is proposed. The theory of multi-stage common-source (CS) configuration as an auxiliary amplifier to enhance the bandwidth and output impedance of RGC topology is analyzed. Additionally, negative Miller capacitance and shunt active inductor compensation are exploited to further expand the bandwidth. The proposed RGC TIA is simulated based on UMC 0.18 µm standard CMOS process. The simulation results demonstrate that the proposed TIA has a high transimpedance of 60.5 dBΩ, and a -3 dB bandwidth of 5.4 GHz is achieved for 0.5 pF input capacitance. The average equivalent input noise current spectral density is about 20 pA/Hz1/2 in the interested frequency, and the TIA consumes 20 mW DC power under 1.8 V supply voltage. The voltage swing is 460 mVpp, and the saturation input current is 500 µA.

A folded cascade-based broadband transimpedance amplifier for optical communication systems

This paper presents a high gain CMOS transimpedance amplifier (TIA) design using staggering technique to obtain high bandwidth and low gain ripple. To provide the staggered frequency response, the proposed TIA employs a π-network as a transimpedance stage along with a novel Folded Cascade-based shunt amplifier as a post amplifier stage. Simulation of the proposed TIA for 1.8V 0.18μm CMOS technology shows that a gain of 58dBΩ with 1dBΩ gain-ripple over a bandwidth of 8.1GHz can be achieved while the whole TIA circuit consumes 38.2mW from 1.8V power supply. The simulated average input noise current spectral density is about 15pA/Hz within the TIA frequency band.

Low-Noise Front-End Receiver Dedicated to Biomedical Devices: NIRS Acquisition System

This paper concerns the design and the implementation of a fully integrated front-end intended to Near-Infrared Spectroscopy System (NIRS) acquisition system. A low-noise transimpedance amplification (TIA) circuit followed by adjustable cut-off frequency and a low-pass filter (LPF) was implemented in order to decrease noise circuit of NIRS detectors. For TIA, a single ended common source, common gate input stage based on a cascode structure is used to get a higher gain-bandwidth closed-loop transimpedance amplifier. To enhance the circuit noise performance, a single feedback transistor technique is used, compared to passive feedback, to achieved high quality data from NIRS acquisition channel. The proposed LPF combines two control methods to adjust the low cut-off frequency. Simulation results show a TIA gain of 104.2 dBΩ, ?3dB bandwidth of 19 MHz and an equivalent input noise current spectral density of 446 fA/√Hz. LPF filter exhibits a relatively constant noise 201nV/√HzQUOTE√Hz from 0 Hz to 700 KHz and linearity performance over its entire tuning range. The proposed front-end of NIRS preamplifier is implemented using 0.18 μm CMOS technology.

1-Gb/s zero-pole cancellation CMOS transimpedance amplifier for Gigabit Ethernet applications

A zero-pole cancellation transimpedance amplifier (TIA) has been realized in 0.35 μm RF CMOS technology for Gigabit Ethernet applications. The TIA exploits a zero-pole cancellation configuration to isolate the input parasitic capacitance including photodiode capacitance from bandwidth deterioration. Simulation results show that the proposed TIA has a bandwidth of 1.9 GHz and a transimpedance gain of 65 dB·Ω for 1.5 pF photodiode capacitance, with a gain-bandwidth product of 3.4 THz·Ω. Even with 2 pF photodiode capacitance, the bandwidth exhibits a decline of only 300 MHz, confirming the mechanism of the zero-pole cancellation configuration. The input resistance is 50 Ω, and the average input noise current spectral density is 9.7 pA/√Hz. Testing results shows that the eye diagram at 1 Gb/s is wide open. The chip dissipates 17 mW under a single 3.3 V supply.

Using High Frequency Operational Amplifiers for Low Noise Design

In this paper we present a comprehensive noise and stability analysis of both the current feedback and the voltage feedback op-amp when connected as transimpedance amplifiers with capacitive current sources. It is generally assumed that the current feedback op-amp is noisier than the voltage feedback op-amp; we show how external component values play an important role in determining the total equivalent input noise current spectral density and show that the voltage feedback op-amp may, in certain cases, be noisier than the current feedback op-amp. Both amplifier types are compared in terms of stability, noise and bandwidth; we find that the current feedback op-amp is particularly suited for operation as a transimpedance amplifier. Theoretical analysis is confirmed by simulations of equivalent circuits of the current feedback op-amp and the voltage feedback op-amp, and simulations of the macro models of two high performance commercially available op-amps, namely the Elantec EL2260 current feedback op-amp and the Elantec EL2244 voltage feedback op-amp.

Monolithic AGC loop for a 160 Mb/s transimpedance amplifier

A new BiCMOS monolithic automatic gain control (AGC) amplifier with wide dynamic range is described. The forward gain path has 120 k/spl Omega/ transimpedance, 140 MHz bandwidth, input noise current spectral density of 1.17 pA//spl radic/Hz and input signal current handling capability of 4 mA. An on-chip peak detector incorporating a 25 pA current source yields AGC hold times in the millisecond range.

A wideband low-noise variable-gain BiCMOS transimpedance amplifier

A new monolithic variable gain transimpedance amplifier is described. The circuit is realized in BiCMOS technology and has measured gain of 98 k/spl Omega/, bandwidth of 128 MHz, input noise current spectral density of 1.17 pA//spl radic/(Hz) and input signal-current handling capability of 3 mA.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Less than 3 pA/√Hz over 1–800 MHz noise current spectral density optical receiver for SCM-CATV systems

A low noise optical receiver for SCM-CATV systems is described which uses discrete, commercial devices. By using a symmetrical resonance tuned input configuration, the equivalent input noise current spectral density, measured according to an accurate method, is less than 3 pA/√Hz in the frequency range 1–800 MHz.