用于红外焦平面读出电路的新型输出缓冲器

根据红外焦平面读出电路输出缓冲器的大输出摆幅和大压摆率的特点,设计了一种应用于红外焦平面读出电路的新型输出缓冲器,由于输出缓冲器需要一个较大的输出摆幅,所以采用轨对轨输入以及AB类输出的全差分运放,使其在不损失增益的情况下提高带宽和输出摆幅;并在轨对轨结构中插入恒定跨导电路,使电路更加稳定;在输出缓冲器高压摆率的要求下...     

一种恒跨导轨对轨CMOS运算放大器的设计

设计了一种新颖的恒跨导轨对轨CMOS运算放大器结构。输入级采用轨对轨的结构,在输入级采用4个虚拟差分对管来对输入差分对的电流进行限制,使运放的输入级跨导在工作范围内保持恒定。输出级采用前馈式AB类输出结构,以使输出达到全摆幅。仿真结果显示,在5 V电源电压和带有10 pF电容与10 kΩ电阻并联的负载下,该运放在共模输入范围内实现了恒跨导,在整个共模输入范围内跨导变化率仅为3%,输出摆幅也达到了轨对轨全摆幅,运放的开环增益为108.5 dB,增益带宽积为26.7 MHz,相位裕度为76.3°。     

铁电栅材料GaN基场效应晶体管的特性

针对铁电薄膜/GaN基FET结构,利用数值方法研究了铁电栅材料自发极化强度PS变化对GaN基表面电子浓度nS和场效应晶体管转移特性Id-Vg的影响,给出了典型PS和εr值下跨导gm与Vg的关系。结果表明:零栅压下,nS在随PS(0～±59μC/cm2)变化时有4～6个数量级的提高或降低;当Vg=0.65V、PS为-26～26μC/cm2时,nS提高约4个数量级;负栅压下,nS因受引起电子耗尽的PS的影响而降低6～7个数量级,而PS未对Id-Vg产生明显影响,跨导gm在1V左右的栅偏压下达到最大值。这些结果对利用铁电极化和退极化可能改善新型器件性能的研究具有重要意义。     

一种3 V CMOS恒跨导运算放大器的设计

提出了一种适合在3V电源电压下工作的CMOS运算放大器，其动态工作范围为0-3V，在整个工作范围内，运算放大器的跨导基本保持不变，给出了BSIM3V3模型下的Hspice模拟结果。     

A low-noise widely tunable Gm-C filter with frequency calibration

A fourth-order Gm-C Chebyshev low-pass filter is presented as channel selection filter for reconfigurable multi-mode wireless receivers. Low-noise technologies are proposed in optimizing the noise characteristics of both the Gm cells and the filter topology. A frequency tuning strategy is used by tuning both the transconductance of the Gm cells and the capacitance of the capacitor banks. To achieve accurate cut-off frequencies, an on-chip calibration circuit is presented to compensate for the frequency inaccuracy introduced by process variation. The filter is fabricated in a 0.13 μm CMOS process. It exhibits a wide programmable bandwidth from 322.5 kHz to 20 MHz. Measured results show that the filter has low input referred noise of 5.9 nV/√Hz and high out-of-band ⅡP3 of 16.2 dBm. It consumes 4.2 and 9.5 mW from a 1 V power supply at its lowest and highest cut-off frequencies respectively.     

A fully integrated CMOS inverse sine circuit for computational systems

An inverse trigonometric function generator using CMOS technology is presented and implemented. The development and synthesis of inverse trigonometric functional circuits based on the simple approximation equations are also introduced. The proposed inverse sine function generator has the infinite input range and can be used in many measurement and instrumentation systems. The nonlinearity of less than 2.8% for the entire input range of 0.5 Vp-p with a small-signal bandwidth of 3.2 MHz is achieved. The chip implemented in 0.25 μm CMOS process operates from a single 1.8 V supply. The measured power consumption and the active chip area of the inverse sine function circuit are 350 μW and 0.15 mm², respectively.     

A high-order curvature compensation technique for bandgap voltage reference using subthreshold MOSFETs

A bandgap voltage reference with high-order curvature compensation is presented in this study. It exploits subtraction and derivative equalisation of currents generated from two complementary NMOS and PMOS bandgap references (BGRs) using subthreshold MOSFETs. By equating the derivative with respect to temperature of the two currents, generated by the complementary bandgaps, and subtracting these currents, an accurate high-order curvature compensation is achieved. To overcome problems due to the limited input common-mode range of opamps used in BGRs, a transimpedance amplifier with new accurate current compensation that tracks the temperature variation is proposed. This bandgap is implemented using the 0.18 μm CMOS process with a supply voltage as low as 0.7 V. At 0.8 V power supply and an output reference voltage of 386 mV, the proposed circuit achieves a temperature coefficient of 19 ppm/°C from 0 to 130°C. The power consumption is 119 μW and the power supply reduction ratio is 24 dB at 1 kHz.     

A new analytical subthreshold model of SRG MOSFET with analogue performance investigation

For the first time, a pseudo-two-dimensional (2D) approach is extended from a rectangular device structure to a cylindrical one. A pseudo-2D model applying Gauss's law in the cylindrical channel depletion region for undoped or lightly doped surrounding gate (SRG) silicon metal oxide semiconductor field effect transistor (MOSFETs) working in subthreshold regime is presented. From this pseudo-2D analysis, electrostatic potentials, current characteristics, the threshold voltage roll-off, the drain-induced barrier lowering and the subthreshold swing are explicitly modelled. The obtained analytical model has been extended to develop a model for transconductance-to-drain current ratio (g _m/I _d) in weak inversion regime. Analogue figures of merit of SRG MOSFETs are studied, including transconductance efficiency g _m/I _d, intrinsic gain and output resistance. The trends related to their variations along the downscaling of dimension are provided. In order to validate our model, the modelled expressions are compared with the simulated characteristics obtained from ATLAS device simulator.     

Multiple-input single-output low-input and high-output impedance current-mode biquadratic filter employing five modified CFTAs and only two grounded capacitors

This paper presents a novel current-mode biquadratic filter with three inputs and a single output. The proposed circuit employs five modified current follower transconductance amplifiers (MCFTAs) and only two grounded capacitors. It can realize all five biquadratic filter functions namely: low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) at the output terminal by selecting different input current signals, without requiring any parameter-matching conditions or additional circuits. The filter has an orthogonal electronic adjustment of the natural angular frequency ω₀ and the quality factor Q, and it has very low element sensitivities of ω₀ and Q. Moreover, the proposed filter has the feature of high output impedance and low input impedance, and the use of only grounded capacitors makes it convenient for integrated circuit implementation. The performances of the proposed circuit are illustrated by PSPICE simulations, and the results are in good agreement with theoretical analysis.     

Design of high-order elliptic filter from a versatile mode generic OTA-C structure

A new synthesis methodology for high-order versatile mode programmable Operational transconductance amplifier and capacitor (OTA-C) generic filter structure is proposed. The structure fulfills the three main criteria of high frequency operation i.e it uses (1) less number of components (2) only single ended input OTAs (3) only grounded capacitors. Any nth order transfer function can be realised from it. Elliptic filter is designed from the generic structure using optimisation technique to reduce the number of OTAs. SPICE simulation with BSIM level 53 model and 0.13 μm process confirms the theoretical analysis. Frequency response of third-order and fourth-order elliptic filter is shown as representative set of simulated result. Sensitivity and non-ideal effect of the designed filter are studied.