Design for testability of embedded integrated operationalamplifiers

The operational amplifier (op amp) is one of the most encountered analog building blocks. In this paper, the problem of testing an integrated op amp is treated. A new low-cost vectorless test solution, known as oscillation test, is investigated to test the op amp. During the test mode, the op amps are converted to a circuit that oscillates and the oscillation frequency is evaluated to monitor faults. The tolerance band of the oscillation frequency is determined using a Monte Carlo analysis taking into account the nominal tolerance of all important technology and design parameters. Faults in the op amps under test which cause the oscillation frequency to exit the tolerance band can therefore be detected. Some Design for Testability (DfT) rules to rearrange op amps to form oscillators are presented and the related practical problems and limitations are discussed. The oscillation frequency can be easily and precisely evaluated using pure digital circuitry. The simulation and practical implementation results confirm that the presented techniques ensure a high fault coverage with a low area overhead     

Chaotic Oscillators Derived from Sinusoidal Oscillators Based on the Current Feedback Op Amp

A collection of novel chaotic oscillators displaying behavior similar to that of the chaotic Colpitts oscillator and requiring the same number and type of energy storage elements is proposed. The oscillators use as an active element the current feedback op amp (CFOA) mostly employed as a current negative impedance converter (INIC). Nonlinearity is introduced through a two-terminal voltage-controlled nonlinear device with an antisymmetric driving-point characteristic. The chaos generators are designed based on sinusoidal oscillators that have been modified for chaos in a semi-systematic manner. By using CFOAs, several attractive features are attained, in particular suitability for high frequency operation. Systems of third- and fourth-order ordinary differential equations describing the chaotic behaviors are derived. Experimental results, PSpice circuit simulations and numerical simulations of the derived mathematical models are included.     

High Dynamic Range Variable Fiber-Optical Attenuator Using Digital Micromirrors and Opto-Fluidics

To the best of the authors knowledge, proposed is the first variable fiber-optical attenuator (VFOA) using a digital micromirror device (DMD) and an opto-fluidic electronically controlled variable focus lens (ECVFL). The hybrid VFOA uses individually controllable two-state micromirrors of the DMD and the variable focal length capability of the ECVFL to control the amount of light coupled between two fiber ports leading to a high dynamic range VFOA. The demonstrated VFOA at 1545 nm has a 63.5-dB dynamic range, $≪$0.1-dB resolution, 0.2-dB polarization-dependent loss, 4.9-dB optical loss, and $≪$ 100-ms switching time. Applications for the proposed VFOA include use in test and measurement systems.      

Broadband All-Digital Variable Fiber-Optic Attenuator Using Digital Micromirror Device

To the best of our knowledge, we propose the first broadband variable fiber-optic attenuator (VFOA) using a digital micromirror device (DMD). The VFOA design is based on a unique double reflection geometry structure that counters the strong spectral attenuation inherent when implementing single-mode-fiber light coupling via a pixelated blazed grating device such as a DMD. The demonstrated VFOA features ~C-band 1530- to 1560-nm broadband attenuation operation with a plusmn0.17-dB in-band variation and a 25-dB attenuation dynamic range. This high repeatability all-digital VFOA can be useful in broadband optical source controls, test instrumentation, telecommunications, signal processing, and sensor systems.     

RC oscillators with oscillation frequency independent of the op.-amp. gain-bandwidth product

Applying the determining equation proposed by Chua and Tang (1982), a frequency sensitivity problem in RC op.-amp. based oscillators is considered. A new expression for the sensitivity of oscillation frequency, ω_o, to changes in any oscillator parameter is developed. Then, the condition for this frequency to be insensitive to changes in the gain-bandwidth products (GB) of the op.-amp. used in the oscillator is formulated. Examples of two circuits exhibiting a zero sensitivity of ω_o to the GB changes (a very desirable feature) are presented. The first example represents oscillators with a single op.-amp. whose slew-rate effect is the only oscillator non-linearity. The second example concerns oscillators with a so-called composite amplifier where non-linear elements included in the oscillator feedback network are responsible for amplitude stabilization.     

低功耗恒定跨导轨对轨运算放大器设计技术研究

为了解决轨对轨运算放大器输入级跨导随共模输入电压变化的影响,采用实时共模电压监测技术,动态跟踪轨对轨运放输入级的跨导变化,通过对偏置电流的高精度定量补偿,从而实现了对输入级跨导的恒定性控制。基于0.18μm CMOS工艺进行了具体电路的设计实现,结果表明:在电源电压3.3 V、负载电阻100Ω、负载电容1 nF的条件下,运放增益为148 dB、相位裕度为61°、功耗为39.6μW,共模输入范围高达0~3.3 V,输入级跨导变化率仅为2.1%。     

High-speed GaAs operational amplifier

An operational amplifier has been designed and fabricated using GaAs MESFETs. This amplifier is a general-purpose monolithic GaAs op amp designed as as a stand-alone component. The amplifier has a differential input, an open-loop gain in excess of 60 dB, and is internally compensated. The high open-loop gain (60 dB at 100 kHz) was achieved by using gain stages with positive feedback. The op amp incorporates a current-mirror level-shifting stage which allows the op amp to operate over a wide power-supply range (/spl plusmn/5-9 V). Previous designs have diodes to achieve level shifting, a practice that precludes operation over a wide supply range. This op amp is a true analog to its silicon counterparts, but it has a higher gain-bandwidth product.     

共源共栅CMOS运算放大器的分析与设计

本文描述了一个共源共栅差分输入级、电流镜偏置输出级结构的两级CMOS运放,它对常规运放的电源电压抑制比、增益、输出驱动能力、噪声、失调等有显著的改善。文中对运放的工作原理及设计技术等进行了详细的叙述,并采用标准CMOS工艺进行了投片试制和采用SPICE进行了电路模拟。结果令人满意,达到了设计指标,证明了设计理论的正确性。该运放已成功地应用于开关电容滤波器芯片的制造。     

The response of 741 op amps to very short pulses

A 741 op amp behaves like a monostable multivibrator when very short pulses are applied to the noninverting input terminal. It is shown that perturbations on the power supply lines or at the output of the amplifier will directly or indirectly have the same effect on the op amp.     

Distortion in single-, two- and three-stage amplifiers

Nonlinear distortion in single-, two-, and three-stage operational amplifiers (opamps) is the main scope of this paper. For each opamp, distortion contributions from different groups of transistors are identified and plotted versus frequency. This makes it possible to find the strongest sources of distortion in the various frequency regions. Further, equations that describe the third harmonic as a function of circuit parameters and input frequency are presented. Despite the simplifications, these equations describe the third harmonic accurately. Further, they provide insight and understanding by connecting distortion to circuit parameters such as transconductances, capacitances, poles, and zeros. The comparison of the opamps shows that each opamp has a frequency region where the distortion is lower than for the other two. The three-stage op amp has far lower distortion at low frequencies, the single-stage op amp is better at high frequency and the two-stage op amp is best for the mid frequency range.     

基于ATmega16单片机的数控稳压电源设计

设计一款基于ATmega16单片机的精密数控稳压电源,该单片机内置PWM方波发生器,内置10BIT高精度兰A/D转换器,采用LM317作功率调整器件,高速运放TL084作反馈控制单元,实现电压0-20V连续可调,调整精度±0.01V,最大允许电流2A,分辨率0.01A,输出纹波电压低于100mV,具有恒流输出功能.     

A dual current feedback op amp in CMOS technology

A CMOS circuit configuration implementing a current feedback or transimpedance op amp (CFB op amp) is presented. The architecture of the circuit is derived from similar bipolar CFB op amps. The properties of the CMOS implementation are similar to those of its bipolar counterparts, i.e., a high slew rate and a bandwidth which is independent of the closed-loop gain when the op amp is used with current feedback. Further, it is shown how two CFB op amps can be connected to achieve a non-slew-rate-limited voltage-mode op amp.     

一种高电源抑制比带隙基准电压源的设计

设计了一种基于反馈电路的基准电压电路。通过正、负两路反馈使输出基准电压获得了高交流电源抑制比(PSRR),为后续电路提供了稳定的电压。采用NPN型三极管,有效消除了运放失调电压对带隙基准电压精度产生的影响,并对电路进行温度补偿,大大减小了温漂。整个电路采用0.35μm CMOS工艺实现,通过spectre仿真软件在室温27℃、工作电压为4 V的条件下进行仿真,带隙基准的输出电压为1.28 V,静态电流为2μA,在-20~80℃范围内其温度系数约为18.9×10-6/℃,交流PSRR约为-107 dB。     

Compact High Gain CMOS Op Amp Design using Comparators

This paper discusses the design of high gain, general purpose op amps. The op amp is based on a novel cascaded design using comparators and with structural simplicity approaching that of digital circuits. Ideally, the design tool presented here can be used to optimize gain and CMRR independent of the other op amp performance parameters. The designed op amp has 140 dB open-loop gain and 43 MHz unity gain frequency (GBW) in Berkeley Spice3f Level-2 simulation. The circuit is implemented using a 2.0 m nwell CMOS process through MOSIS. The op amp is self-biased and requires only power supplies of ±2.5 V. It occupies an area of 113 m×474 m.     

The design of fully differential CMOS operational amplifiers without extra common-mode feedback circuits

A new fully differential CMOS operational amplifier (op amp) without extra common-mode feedback (CMFB) circuit is proposed and analyzed. In this op amp, simple inversely connected current-mirror pairs are used as active loads. From the theoretical analysis, it is shown that the common-mode signal can be efficiently suppressed by the reduced effective common-mode resistance of the active load. The proposed op amp with 2 pF capacitance loadings has an open-loop unity-gain bandwidth of 63 MHz, a phase margin 47°, and a dc gain of 67 dB in 3.5µm p-well CMOS technology. The common-mode gain at a single output node can be as low as —38 dB without extra CMFB circuit. Experimental results have successfully confirmed the capability of the efficient common-mode rejection.This work was supported by the United Microelectronics Corporation (UMC), Republic of China, under Grant C80054.     

Changing technology-banish the 741! [op amp]

Pick up a current electronics text and you're likely to find the 741 op amp not only used, but also showcased. It's the op amp of choice for lab experiments, treatment of innards, etc. This is truly amazing when you consider that the 741 is nearly 30 years old! Of course op amps should be presented they can be used to implement a remarkable range of circuit functions. An inexpensive op amp can give near-ideal performance in certain practical applications. Getting something to work is infectious-the first op amps gave a whole generation the opportunity to build analog functions that really worked. But, like all technologies, op amp development never ceased; there have been some serious developments over the last 30 years!     

Predicting the Effect of Pulsed Ionizing Radiation on Operational Amplifiers

The response of IC operational amplifiers (op amps) to pulsed ionizing irradiation is studied theoretically and experimentally. The major mechanisms of the radiation response are covered. The contributions of main op-amp stages to the output-voltage response are analyzed. The ionization-induced failure of an op amp is traced to its intermediate stages. It is established that the recovery time depends on the type of compensation employed. A block-model approach is proposed as a method for the prediction of transient radiation responses. Ways to define the performance index of an op amp exposed to pulsed ionizing radiation are discussed.     

High-gain gaas mesfet op amp

A gain enhancement technique for GaAs MESFET op amps is presented. It uses positive feedback to cancel the output conductance between the driver and active load transistors in a common-source amplifier configuration. An op amp using this technique was implemented in a 1-µm non-self-aligned GaAs MESFET process. The op amp exhibited a dc gain of 60 dB and a unity-gain frequency of 840 MHz.Please address all correspondence to C.A.T. Salama.     

Digital-Compatible Testing Scheme for Operational Amplifier

This paper presents a digital-compatible testing scheme for operational amplifier (op amp). In the proposed scheme, the op amp device under test (DUT) is configured to a unity-gain buffer which is responded to a testing pulse, could be realized by a ring oscillator circuit. The output of the configured unity-gain buffer is digitized by simple digital counter and then the digitized counting number is compared to a predetermined critical value to evaluate the op amp DUT. The digitized counting number is sensitive to the specification of op amp DUT and easily to be observed in the digital domain. The testing parameters of testing setup of stimulus, testing result, testing accuracy, and testing time are also investigated to detail the proposed scheme. Digital compatibility and simplicity are main advantages of the proposed testing scheme. In addition, no complicated analog comparator and reference voltages are required. Behavioral and circuit level simulations are performed to show the effectiveness of the proposed scheme.     

单电源运放的偏置原因分析与偏置方法

运放是模拟电路中的核心元件,近些年来单电源运放因其正常工作时只需提供单路电源的独特优点而应用日益广泛。但是单电源运放的设计却比双电源运放复杂。因此对单电源运放偏置的原因进行了深入的研究,并分析比较了各种不同偏置方法的特点,从而为正确分析和设计单电源运放偏置电路提供依据。