Search Results (74)

In high-precision Hemispherical Resonator Gyroscope (HRG) control systems, readout circuit noise critically determines resonator displacement detection precision. Addressing noise issues, this paper compares the noise characteristics and contribution mechanisms of the Transimpedance Amplifier (TIA) and Charge-Sensitive Amplifier (CSA). By establishing a noise model and analyzing circuit bandwidth, the dominant role of feedback resistor thermal noise in the TIA is revealed. These analyses further demonstrate the significant suppression of high-frequency noise by the CSA capacitive feedback network. Simulation and experimental results demonstrate that the measured noise of the TIA and CSA is consistent with the theoretical model. The TIA output noise is 25.8 $\mathsf{\mu }{V}_{\mathrm{rms}}$, with feedback resistor thermal noise accounting for 99.8%, while CSA output noise is reduced to 13.2 $\mathsf{\mu }{V}_{\mathrm{rms}}$, a reduction of 48.8%. Near resonant frequency, the equivalent displacement noise of the CSA is $1.69\times {10}^{-14}\mathrm{m}/\sqrt{\mathrm{Hz}}$, a reduction of 86.7% compared to the TIA’s $1.27\times {10}^{-13}\mathrm{m}/\sqrt{\mathrm{Hz}}$, indicating the CSA is more suitable for high-precision applications. This research provides theoretical guidance and technical references for the topological selection and parameter design of HRG readout circuits. Full article

This paper presents a CMOS-based optoelectronic receiver integrated circuit (CORIC) realized in a standard 180 nm CMOS technology for the applications of short-distance optical interconnects. The CORIC comprises a spatially modulated P⁺/N-well on-chip avalanche photodiode (P⁺/NW APD) for optical-to-electrical conversion, a dummy APD at the differential input for enhanced common-mode noise rejection, a cross-coupled differential transimpedance amplifier (CCD-TIA) for current-to-voltage conversion, a 3-bit continuous-time linear equalizer (CTLE) for adaptive equalization by using NMOS registers, and a $f_T$-doubler output buffer (OB). The CTLE and $f_T$-doubler OB combination not only compensates the frequency-dependent signal loss, but also provides symmetric differential output signals. Post-layout simulations of the proposed CORIC reveal a transimpedance gain of 53.2 dBΩ, a bandwidth of 4.83 GHz even with a 490 fF parasitic capacitance from the on-chip P⁺/NW APD, a dynamic range of 60 dB that handles the input photocurrents from 1 μA_pp to 1 mA_pp, and a DC power consumption of 33.7 mW from a 1.8 V supply. The CORIC chip core occupies an area of 260 × 101 μm². Full article

This study introduces an electronically tunable resistorless mixed-mode universal filter and dual-mode quadrature oscillator configuration utilizing merely two voltage differencing gain amplifiers and two grounded capacitors. The suggested filter can perform all generic biquadratic filter functions in all four modes: voltage mode, trans-admittance mode, current mode, and trans-impedance mode, while utilizing the same design. The pole frequency and the quality factor can be tuned electronically and orthogonally by means of the transconductances of the voltage differencing gain amplifier. The dual-mode quadrature oscillator featuring both voltage and current outputs can also be obtained from the proposed filter core. It additionally provides separate electronic control of the oscillation condition and frequency. Several PSPICE simulations with the TSMC 0.18 μm CMOS model confirm the feasibility of the proposed configurations. Both proposed circuits were experimentally evaluated using commercially available integrated circuit LM13600s. Both simulation and experimental results have validated the performance of the design. Full article

The four-quadrant detector (4QD), as a highly sensitive and fast-response position-sensitive device, is widely used in laser guidance, target tracking, and related fields. However, traditional visible and infrared 4QDs exhibit significant vulnerability to ambient light interference, particularly under high-intensity background illumination. To address this issue, this paper presents a solar-blind ultraviolet (UV) 4QD and a spot positioning system based on AlGaN diodes, achieving a UV/visible suppression ratio of 2.17 × 10⁴ (without solar-blind filters). The system employs a high-linearity, low-noise capacitive transimpedance amplifier (CTIA) as the readout circuit for the high-sensitivity and rapid-response solar-blind UV detectors, enabling the precise conversion of weak photocurrent signals into voltage signals for digitization. Utilizing a third-order polynomial least-squares fitting algorithm without introducing complex filtering techniques, the system achieves a maximum positioning error of 0.0101 mm and a root-mean-square error (RMSE) of 0.0057 mm, among of one the best-performing solar-blind UV 4QDs. The experimental results demonstrate exceptional spot positioning performance under a 275 nm laser source, meeting the high-precision requirements for space target detection. This research provides a reference for the application of solar-blind UV 4QDs in positioning, alignment, and monitoring scenarios, thereby holding significant practical implications. Full article

Semiconductor radiation detectors usually use a specific signal conditioning circuit, ensuring the required detection system parameters. This paper details the noise properties of specific input stages in photoreceivers that detect various types of radiation. For this purpose, the popular silicon PIN photodiode (BPW34) and two different types of low-noise operational amplifiers (AD797A and ADA4625-1) were used. In the presented experiments, noise measurements were provided for voltage and transimpedance amplifiers operating in input stages, comparing their noise and bandwidths. This made it possible to obtain results for bipolar junction transistor (BJT)- and field-effect transistor (FET)-based input stages of circuity, cooperating directly with a photodiode. Analyzing the obtained characteristics and considering the photodiode operation mode, it is evident that the transimpedance amplifier and photoconductive mode should be considered a typical first-choice solution. In some cases, the performances, such as bandwidth and noise, may be similar to those of voltage. Nevertheless, the bias method used in TIA and feedback compensation can also affect the resulting output noise spectral characteristics due to the photodiode and other capacitances existing in the circuit. In the case of a high transimpedance, the FET-based op-amps ensure lower output noise than the BJT-based ones due to the significantly lower current noise. The simple radiation detector with two-channel differential TIA was also proposed and tested based on the results obtained. Full article

Silicon photodetectors are well developed, with the advantage of their low cost and easy fabrication. However, due to the semiconductor band gap limitation, their detection wavelength is limited in the visible and near-infrared ranges. To broaden the detection wavelength, we stacked a mercury telluride (HgTe) colloidal quantum dot (CQD) photodiode and a silicon PIN photodiode in series. This detector shows response spectra ranging from visible to short-wave infrared (430 nm to 2800 nm) at room temperature. At zero bias, the total photocurrents are 112.5 μA and 1.24 μA, with a tungsten lamp and a blackbody serving as light sources, respectively. The response speed can reach 1.65 μs, with the calculated detectivities of the visible wavelength D* = 1.01 × 10¹¹ Jones, and that of the short-wave infrared being D* = 2.66 × 10¹⁰ Jones at room temperature. At the same time, with a homemade trans-impedance amplifier (TIA) circuit, we demonstrate the device application for figuring out the amplified voltage of the VIS, SWIR, and the VIS-SWIR stacked layers. Full article

This paper presents a low-noise CMOS transimpedance-limiting amplifier (CTLA) for application in LiDAR sensor systems. The proposed CTLA employs a dual-feedback architecture that combines the passive and active feedback mechanisms simultaneously, thereby enabling automatic limiting operations for input photocurrents exceeding 100 µA_pp (up to 1.06 mA_pp) without introducing signal distortions. This design methodology can eliminate the need for a power-hungry multi-stage limiting amplifier, hence significantly improving the power efficiency of LiDAR sensors. The practical implementation for this purpose is to insert a simple NMOS switch between the on-chip avalanche photodiode (APD) and the active feedback amplifier, which then can provide automatic on/off switching in response to variations of the input currents. In particular, the feedback resistor in the active feedback path should be carefully optimized to guarantee the circuit’s robustness and stability. To validate its practicality, the proposed CTLA chips were fabricated in a 180 nm CMOS process, demonstrating a transimpedance gain of 88.8 dBΩ, a −3 dB bandwidth of 629 MHz, a noise current spectral density of 2.31 pA/√Hz, an input dynamic range of 56.6 dB, and a power dissipation of 23.6 mW from a single 1.8 V supply. The chip core was realized within a compact area of 180 × 50 µm². The proposed CTLA shows a potential solution that is well-suited for power-efficient LiDAR sensor systems in real-world scenarios. Full article

This paper presents an optoelectronic transceiver (OTRx) realized in a 180 nm CMOS technology for applications of short-range LiDAR sensors, in which a modified current-mode single-ended VCSEL driver (m-CMVD) is exploited as a transmitter (Tx) and a voltage-mode fully differential transimpedance amplifier (FD-TIA) is employed as a receiver (Rx). Especially for Tx, a concurrent automatic power control (APC) circuit is incorporated to compensate for the inevitable increase in the threshold current in a VCSEL diode. For Rx, two on-chip spatially modulated P⁺/N- well avalanche photodiodes (APDs) are integrated with the FD-TIA to achieve circuit symmetry. Also, an extra APD is added to facilitate the APC operations in Tx, i.e., concurrently adjusting the bias current of the VCSEL diode by the action of the newly proposed APC path in Rx. Measured results of test chips demonstrate that the proposed OTRx causes the DC bias current to increase from 0.93 mA to 1.42 mA as the input current decreases from 250 µA_pp to 3 µA_pp, highlighting its suitability for short-range sensor applications utilizing a cost-effective CMOS process. Full article

The nonlinearity problem of digital pixels restricts the reduction in power consumption at the pixel-level circuit. The main cause of nonlinearity is discussed in this article and low power consumption is attained by reducing the static current in capacitive transimpedance amplifiers (CTIAs) and comparators. Linearity was successfully improved through the use of an off-chip calibration method. A 64 × 64 array prototype digital readout integrated circuit (DROIC) was fabricated using a 0.18 μm 1P6M CMOS process. Experimental results indicated that the post-calibration linearity reached 99.6% with an input current of up to 1.5 μA. The static power consumption per digital pixel was 6 μW. Full article

The reliability of inverse-mode silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) under dc stress and its potential impact on the performance of basic analog amplifiers are investigated. In order to properly reflect the stress effects in various circuit applications, the degradations under three different configurations (active bias, diode connection, and off state) were experimentally characterized with the stress voltages applied up to 3000 s for each case. Based on the changes in the Gummel response, the degradations in device parameters such as current gain (β), transconductance (g_m), and base-to-emitter resistance (r_π) were extracted and compared with the forward-mode counterpart. In addition, with the use of a small-signal equivalent model of a SiGe HBT, simple single-stage analog amplifiers were simulated as representative examples and their circuit-level performance metrics including gain and bandwidth were studied to estimate degradation characteristics with accumulated stress. It was found that transimpedance gain decreases and operation bandwidth increases to different levels due to device degradation, whereas a voltage amplifier exhibited much less changes. Full article

This paper presents a novel optoelectronic transimpedance amplifier (OTA) for short-range LiDAR sensors used in 180 nm CMOS technology, which consists of a main transimpedance amplifier (m-TIA) with an on-chip P⁺/N-well/Deep N-well avalanche photodiode (P⁺/NW/DNW APD) and a replica TIA with another on-chip APD, not only to acquire circuit symmetry but to also obtain concurrent automatic gain control (AGC) function within a narrow single pulse-width duration. In particular, for concurrent AGC operations, 3-bit PMOS switches with series resistors are added in parallel with the passive feedback resistor in the m-TIA. Then, the PMOS switches can be turned on or off in accordance with the DC output voltage amplitudes of the replica TIA. The post-layout simulations reveal that the OTA extends the dynamic range up to 74.8 dB (i.e., 1 µA_pp~5.5 mA_pp) and achieves a 67 dBΩ transimpedance gain, an 830 MHz bandwidth, a 16 pA/$\surd \mathrm{Hz}$ noise current spectral density, a −31 dBm optical sensitivity for a 10⁻¹² bit error rate, and a 6 mW power dissipation from a single 1.8 V supply. The chip occupies a core area of 200 × 120 µm². Full article

This paper presents a mixed-mode universal filter using differential difference current conveyor transconductance amplifiers (DDCCTA). Despite using a minimum number of MOS differential pairs, the proposed DDCCTA is a multiple-input, multiple-output device, that was achieved using the multiple-input bulk-driven MOS transistor (MIBD-MOST) technique, multiple-output current followers and transconductance gains. A subthreshold technique is used to achieve minimum power consumption of the DDCCTA. Thanks to the multiple-input and multiple-output of DDCCTA, the mixed-mode universal filter based on the proposed element can realize five standard filter responses, i.e., low-pass, high-pass, band-pass, band-stop, and all-pass responses, of four modes, i.e., voltage-mode, current-mode, transadmittance-mode, and transimpedance-mode, thus providing 194 filter responses from a single circuit. The natural frequency and quality factor of the filter response can be controlled electronically and orthogonally. The proposed DDCCTA and mixed-mode universal filter are simulated and designed using 0.18 μm CMOS technology to confirm the functionality of the new circuit. The mixed-mode universal filter uses ±0.5 V of supply voltage and consumes 0.374 mW of power when operating at a natural frequency of 10 kHz. Full article

Carbon nanotube field-effect transistors (CNT-FETs) have shown great promise in infrared image detection due to their high mobility, low cost, and compatibility with silicon-based technologies. This paper presents the design and simulation of a column-level analog front-end (AFE) circuit tailored for carbon-based short-wave infrared (SWIR) photodetectors. The AFE integrates a Capacitor Trans-impedance Amplifier (CTIA) for current-to-voltage conversion, coupled with Correlated Double Sampling (CDS) for noise reduction and operational amplifier offset suppression. A 10-bit/125 kHz Successive Approximation analog-to-digital converter (SAR ADC) completes the signal processing chain, achieving rail-to-rail input/output with minimized component count. Fabricated using 0.18 μm CMOS technology, the AFE demonstrates a high signal-to-noise ratio (SNR) of 59.27 dB and an Effective Number of Bits (ENOB) of 9.35, with a detectable current range from 500 pA to 100.5 nA and a total power consumption of 7.5 mW. These results confirm the suitability of the proposed AFE for high-precision, low-power SWIR detection systems, with potential applications in medical imaging, night vision, and autonomous driving systems. Full article

This paper presents a novel power-efficient topology for receivers in short-range LiDAR sensors. Conventionally, LiDAR sensors exploit complex time-to-digital converters (TDCs) for time-of-flight (ToF) distance measurements, thereby frequently leading to intricate circuit designs and persistent walk error issues. However, this work features a fully differential trans-impedance amplifier with on-chip avalanche photodiodes as optical detectors so that the need of the following post-amplifiers and output buffers can be eliminated, thus considerably reducing power consumption. Also, the combination of amplitude-to-voltage (A2V) and time-to-voltage (T2V) converters are exploited to replace the complicated TDC circuit. The A2V converter efficiently processes weak input photocurrents ranging from 1 to 50 μA_pp which corresponds to a maximum distance of 22.8 m, while the T2V converter handles relatively larger photocurrents from 40 μA_pp to 5.8 mA_pp for distances as short as 30 cm. The post-layout simulations confirm that the proposed LiDAR receiver can detect optical pulses over the range of 0.3 to 22.8 m with a low power dissipation of 10 mW from a single 1.8 V supply. This topology offers significant improvements in simplifying the receiver design and reducing the power consumption, providing a more efficient and accurate solution that is highly suitable for short-range LiDAR sensor applications. Full article

A 30~60 GHz broadband down-conversion mixer driven by low local oscillator (LO) power is presented. The down-conversion mixer utilizes an input signal coupling technique based on the Marchand balun to achieve broadband operation and achieves low LO power drive and low DC power consumption through the use of a weak inversion bias with Gilbert switching devices. The broadband conversion of single-ended to differential signals is achieved using the Marchand balun with compensation lines, and an equivalent circuit analysis is performed. For the intermediate frequency (IF) output, a self-biased IF trans-impedance amplifier with current reusing and an active IF balun structure are used to achieve signal amplification and single-ended signal output. Test results show that the proposed mixer achieves a conversion gain of −1.2 to 6.4 dB in an IF output bandwidth of 0.1 to 5 GHz at radio frequency (RF) input frequencies of 30 to 60 GHz and LO driving power of −10 dBm. The DC power consumption of the core mixing unit of the proposed mixer is 4.8 mW, and the DC power consumption including the IF amplifier is 28.3 mW. The proposed mixer uses a 65 nm CMOS technology with a chip area of 0.26 mm². Full article