Transimpedance Amplifier

We have developed a novel analog front-end part of a wireless brain oxymeter receiver instrument based on near-infrared spectroreflectometry (NIRS). The NIRS receiver makes use of dynamic threshold transistors (DTMOS) for low voltage (1–V), low power and low noise enhancement. The design is composed of a transimpedance amplifier (TIA) and an operational transconductance amplifier (OTA). The OTA differential input pairs are in a class AB configuration, and uses DTMOS devices for input common-mode range enhancement. Post-layout simulations under a 5 pF load, using 0.18 µm CMOS technology results are, for the OTA, an input referred noise of 134 nV/√Hz at 1 kHz, and a power consumption of 16.7 µW without any extra noise reduction technique. Also, the TIA gives 208 pA/√Hz at 1 kHz, while having a power consumption of only 10.9 µW. The proposed analog front-end circuits have been used to implement a NIRS receiver instrument with improved ultra low-light level measurements, high resolution...

Trans-impedance amplifier (TIA) are widely used for optical sensing applications (precision instrumentation) and optical communication, such as: fiber optic, IR communication and also Visible Light Communication (VLC). TIA convert the current (I) into voltage (V). Application TIA design depend of objectives requirement system, for high speed as well as highband, low noise, low power and others. This paper explains the empirical experiment of TIA for high-band VLC with over 1- MHz Gain Bandwidth Product (GPWP) estimated. We implement general topology mode: as photovoltaic. The selection of the best resistor feedback (Rf) and compensator (Cf) are presented, we compare simulation approach against real implementation. The OP-AMP chosen from Texas Instruments® product, OPA 656. The TINATM SPICE® simulator used as simulation’s tool. This research contribution lies in applied of engineering design methodology with detailed step to develop major VLC system, we focus on photodiode amplifier only. By depth analysis, can be known next research addresses and obtain the best results without trial and error methods.

This paper presents a CMOS inverter-based class-AB pseudo differential amplifier for HF applications using new simple rail-to-rail CMFB circuit. The proposed circuit employs two CMOS inverters and the complementary common-mode feedback (CMFB) consisting of current mode common-mode detector and transimpedance amplifiers. The circuit has been designed using 0.18 μm CMOS technology under 1 V supply, and the simulation results shows that the rail to rail output swing is achieved with low common-mode gain (-15 dB). The output swing of the circuit is 0.7 V. The power dissipation of the circuit is 96 μW.

VLC is a complex system with lots of challenges in its implementation. One of its problems is noise that originated from internal and external sources (sunlight, artificial light, etc). Internal noise is originated from active components of analog front-end (AFE) circuit, which will be discussed in this paper, especially on the trans-impedance amplifier (TIA) domain. The noise characteristics of AFE circuit in VLC system has been analyzed using the variety of available commercial Op Amp and different types of the photodiode (Si, Si-PIN, Si APD). The approach of this research is based on analytical calculus and simulation using MATLAB®. The results of this research show that the main factor that affecting the noise is e , the feedback resistor (Rf ), and junction capacitor in the photodiode (C). Besides that, the design concept of multi channel TIA (8 channel) using IC Op Amp, with consideration of pin number of each Op Amp, supply needs, the initial value of Rf, converter to 8-DIP and feedback capacitor (Cfj) channel, also discussed
in this paper.

Development of cryogenic readout circuits for Superconducting Tunneling Junction (STJ) direct detectors for submillimeter wave is presented. We chose a Capacitive Transimpedance Amplifier as a preamplifier design for the STJs because of relatively large impedance of the STJ. Using a SONY n-type GaAs Junction Field Effect Transistors (JFET), we measured electrical characteristics of the GaAs JFETs in the temperature range

State-of-the-art 3-D medical ultrasound imaging requires transmitting and receiving ultrasound using a 2-D array of ultrasound transducers with hundreds or thousands of elements. A tight combination of the transducer array with integrated circuitry eliminates bulky cables connecting the elements of the transducer array to a separate system of electronics. Furthermore, preamplifiers located close to the array can lead to improved receive sensitivity. A combined IC and transducer array can lead to a portable, high-performance, and inexpensive 3-D ultrasound imaging system. This paper presents an IC flip-chip bonded to a 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array for 3-D ultrasound imaging. The IC includes a transmit beamformer that generates 25-V unipolar pulses with programmable focusing delays to 224 of the 256 transducer elements. One-shot circuits allow adjustment of the pulse widths for different ultrasound transducer center frequencies. For receiving reflected ultrasound signals, the IC uses the 32-elements along the array diagonals. The IC provides each receiving element with a low-noise 25-MHz-bandwidth transimpedance amplifier. Using a field-programmable gate array (FPGA) clocked at 100 MHz to operate the IC, the IC generated properly timed transmit pulses with 5-ns accuracy. With the IC flip-chip bonded to a CMUT array, we show that the IC can produce steered and focused ultrasound beams. We present 2-D and 3-D images of a wire phantom and 2-D orthogonal cross-sectional images (Bscans) of a latex heart phantom.

An optical preamplifier system consisting of a 27dB-gain erbium-doped fiber amplifier, a three-port circulator and a 47GHz bandwidth in-fiber grating has improved receiver sensitivity and consequently sensor range of a spontaneous Brillouin-based fiber-optic distributed temperature single-ended sensor. Optical signal-to-noise has improved by 17dB. Using this system and operating at 1533nm, a sensor with a range of 23km, spatial resolution of 1.8m, measurement time of 9 minutes and temperature resolution of 6K was implemented. The temperature resolution was attributed to contamination of the backscattered spontaneous Brillouin signal by the residual Rayleigh signal after optical filtering. The optical signal-to-noise is supported theoretically by considering associated noise sources.

This paper reports the design, packaging and characterization of a miniaturized dual-mode radio-frequency (RF)/free space optical (FSO) indoor wireless receiver module. Two different patch antennas are designed and integrated with bare die photodiodes together with transimpedance amplifier (TIA) circuits on a printed circuit board (PCB). Ansoft HFSS is used to predict the coupling from RF to FSO link. Measurement results verify that optical link degradation is minimized with the specially designed patch structure. FSO link operation at 2 Gb/s in a 10 GHz RF environment is achieved. Through the comparison to previously developed RF/FSO modules, the new receiver boards demonstrate reduced RF-to-optical cross channel coupling, and increased gain and antenna radiation efficiency.