Variable-gain Transimpedance Amplifier Research Articles

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.

34-GBd Linear Transimpedance Amplifier for 200-Gb/s DP-16-QAM Optical Coherent Receivers

High spectral efficiency offered by the coherent optical communication links makes them attractive for the next-generation optical communication links. Using advanced modulation schemes such as dual-polarization quadrature-amplitude modulation (DP-QAM) data rates beyond 200 Gb/s can be achieved. A key component of such links is the wide-bandwidth and high-linearity coherent optical receiver. In this paper, we present a fully differential (FD) optical receiver architecture consisting of a variable-gain transimpedance amplifier (VG-TIA) followed by a VG amplifier (VGA). The proposed optical receiver employs a dual-feedback automatic gain control (AGC) loop that controls both the front-end VG-TIA and the following VGA to achieve both low-noise and high-linearity operation. A new photodiode (PD) dc current cancellation scheme is developed and implemented for the full differential front-end TIA. A prototype dual-TIA chip is fabricated in a 0.13- $\mu \text{m}$ SiGe BiCMOS process. The presented TIA achieves 20-pA/ $\sqrt {\text {Hz}}$ input-referred noise (IRN) density, 27-GHz, 3-dB bandwidth, and 1.5% total harmonic distortion (THD) at 1-mApp input PD current and 500-mVpp output voltage swing. This enables the 34-GBd operation with the bit error rate (BER) of $10^{-10}$ and $5.4\times 10^{-4}$ using DP-QPSK and DP-16-QAM formats at optical signal-to-noise ratios (OSNRs) of 25 and 30 dB, respectively, demonstrating the 100- and 200-Gb/s single wavelength optical coherent receiver operation. The dual-TIA chip occupies an area of $1.4\,\,\text {mm}\times 1.6$ mm and consumes 313 mW per channel at 34 GBd from a 3.3-V supply.

Upgrade of the multi-energy soft x-ray diagnostic system for studies of ELM dynamics in the EAST tokamak

The multi-energy soft x-ray (ME-SXR) diagnostic system has been calibrated to study the evolution of the edge electron temperature profile during the edge localized mode (ELM) events. The electronic bandwidth of the Mazet MTi04 multi-channel variable gain trans-impedance amplifier measured in the laboratory is consistent with the nominal value. As the gain of the preamplifier is increased from 105 to 2 × 107, the bandwidth is decreased from 100 kHz to 10 kHz. The relative gain errors for different channels (5 arrays ×20 channels) were also calibrated in situ after the system was installed on the EAST tokamak. The results showed that the relative gain error (RGE) in each array was less than 10% compared to the reference channel of the array, and was insensitive to the preamplifier gains. A feedback loop was designed to automatically adjust the programmable gains of the preamplifiers based on the signal amplitudes measured in the previous discharge. The reconstructed edge electron temperature (Te) profile was also uploaded automatically to the MDSplus server between discharges. Utilizing the fast temporal resolution of Te (∼5 kHz), the dynamics of edge electron temperature evolution during Type I and high frequency ELM (HF-ELM) events were compared. The results showed that the edge Te profile collapsed during Type I ELMs, while for the HF-ELM regime, the edge Te profile pedestal structure sustains stiffness.

A high sensitive 66 dB linear dynamic range receiver for 3-D laser radar

This study presents a CMOS receiver chip realized in 0.18 μm standard CMOS technology and intended for high precision 3-D laser radar. The chip includes an adjustable gain transimpedance pre-amplifier, a post-amplifier and two timing comparators. An additional feedback is employed in the regulated cascode transimpedance amplifier to decrease the input impedance, and a variable gain transimpedance amplifier controlled by digital switches and analog multiplexer is utilized to realize four gain modes, extending the input dynamic range. The measurement shows that the highest transimpedance of the channel is 50 k , the uncompensated walk error is 1.44 ns in a wide linear dynamic range of 66 dB (1:2000), and the input referred noise current is 2.3 pA/ (rms), resulting in a very low detectable input current of 1 μA with SNR = 5.

An in-probe low-noise low-power variable-gain receive amplifier for medical ultrasound imaging using CMUT transducers

In this paper a low-power, low-noise receiver amplifier is designed for interface with capacitive micro-machined ultrasonic transducers (CMUT). In 3D in-probe ultrasound imaging systems, the interface circuit area constraint due to the specified area per CMUT element, and the circuit power constraint for each channel are the main design challenges. A fully-differential variable-gain transimpedance amplifier (VGTIA) is designed for the CMUT signal read-out. Due to the small area and low power consumption, the circuit is suitable for in-probe imaging. The VGTIA is designed for the interface with an ADC block that does the digital conversion inside the probe. The circuit is able to produce a differential output from a Zero-Bias CMUT, where the requirement for an external high voltage dc bias is eliminated. The amplifier is designed and fabricated using a 65 nm CMOS process technology. The measurement results show that the transimpedance amplifier has a gain range of 79---97 dB$$\Omega $$Ω. A noise figure (NF) of 3 dB at a 5 MHz center frequency with an only 180 $$\upmu $$μW power consumption is measured. A total area of 76$$\,\upmu $$μm$$\times $$×50$$\,\upmu $$μm is achieved which relaxes the area requirement for the following ADC block.

A 10 Gb/s Linear Burst-Mode Receiver in 0.25 $\mu$m SiGe:C BiCMOS

This paper presents a 10 Gb/s burst-mode receiver (BMRx) that was designed to have high linearity over a >; 20 dB (optical power) dynamic range. Such a linear BMRx (LBMRx) enables electronic dispersion compensation or multilevel modulation formats in bursty optical links. The LBMRx consists of a variable-gain transimpedance amplifier and a variable-gain post-amplifier. A gain from 47 dBΩ to 85 dBΩ was achieved on a single die. Fast (<; 50ns) gain adjustment is achieved using replica based, feedforward automatic gain control and peak detectors, which are reset between bursts using an external reset signal. A sensitivity of - 23.2 dBm at a bit-error rate of 1.1 × 10-3 was measured using a PIN photodiode. A 0.5 dB penalty is incurred if a 0 dBm burst precedes the burst under consideration; hence the LBMRx can support a dynamic range of 22.7 dB. A 150 ns preamble was used, the guard time between bursts was 25.6 ns. Total harmonic distortion (at 250 MHz) less than 5% was measured for an optical power ranging from - 25ndBm to 0 dBm. The chip was designed in a 0.25 μm SiGe:C BiCMOS technology, has an area of 2.4 × 2.1 mm2 and consumes 650 mW from 2.5 V/3.3 V supplies.

BiCMOS variable gain transimpedance amplifier for automotive applications

A new BiCMOS variable gain transimpedance amplifier with a large area integrated photodiode for automotive applications is presented. Through careful control of the input pole position and the frequency response of the core amplifier, the bandwidth of the transimpedance amplifier varies from 112 to 300 MHz when its gain changes from 14.2 kOmega to 400 Omega. The proposed circuit configuration maintains a high voltage across a common anode photodiode, and its bandwidth in highest gain varies from 121 to 102 MHz over a temperature range of -40 to +140degC. Simulation results in a 0.6 mum Si BiCMOS technology are given. The amplifier consumes 16 mW from a 3.3 V supply.

A CMOS infrared wireless optical receiver front-end with a variable-gain fully-differential transimpedance amplifier

A CMOS infrared wireless optical receiver front-end is presented. A stable variable-gain fully-differential transimpedance feedback amplifier is designed employing a current-mode amplifier as the feedforward gain element. More than a triple variation of the transimpedance gain, from 0.3 k/spl Omega/ to 1 k/spl Omega/, the variable-gain transimpedance amplifier achieves desirable gain-bandwidth independence. For an infrared wireless optical receiver front-end employing the transimpedance amplifier, the optical preamplifier achieves a transimpedance gain of 66 dB/spl Omega/ and a bandwidth of 114 MHz with a 5 pF photodiode capacitance, and a power consumption of 17.4 mW.

A CMOS optical preamplifier for wireless infrared communications

This paper describes a CMOS optical preamplifier suitable for infrared wireless data communications. The preamplifier consists of a differential CMOS variable-gain transimpedance amplifier embedded in a larger feedback loop used to reject photocurrents generated by ambient light. Fabricated in a commercial 0.35-/spl mu/m CMOS process, the preamplifier consumes 8 mW at 3 V, and provides 70 MHz bandwidth over a 77-dB dynamic range with a maximum transimpedance gain of 19 k/spl Omega/. The bandwidth is controlled within a factor of two over a 31-dB variation in gain.

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>