一种新的通用高阶OTA-C滤波器的设计

本文提出以传递函数的信号流图实现为基础,设计出一种新的通用高阶可调OTA-C滤波器.该滤波器仅需要OTA器件和接地电容,适合于用MCS技术实现.实验结果证明了它的可行性.     

基于OTA的多功能电压模滤波器及其仿真

本文采用信号流图法设计了一种基于ＯＴＡ的三输入一输出多功能电压模滤波器新电路，该电路由五个ＯＴＡ和两个接地电容构成，合理选择输入电压可实现低通、高通、带通、带阻及全通滤波功能。文章还对电路进行了ＭＯＳ管级的计算机仿真，其结果表明所提出的电路方案正确有效。     

通用有源电流模式滤波器及其仿真

采用信号流图设计了由两个 OTA和一个 MOCC + / -构成的三输入一输出电流模式二阶滤波器新电路 ,合理选择输入电流可实现低通、高通、带通、带阻及全通滤波功能。所提电路结构简单 ,中心频率ω0 和品质因数 Q独立可调 ,无源元件全部接地 ,滤波器特性参数对无源元件灵敏度低。理论分析和 MOS管级的 PSPICE仿真表明所提电路方案正确     

New high-order filter structures using only single-ended-input OTAs and grounded capacitors

Despite the wealth of literature on operational transconductance amplifier (OTA)-C filters, the synthesis of high-order filter characteristics is still an active topic. In this paper the realization of voltage transfer functions based on canonical current-mode follow-the-leader-feedback (FLF) OTA-C structures are investigated. Two new structures are presented, which use only single-ended-input OTAs and grounded capacitors. The first structure has a single voltage input and multiple voltage outputs taken from different nodes, which enables it to provide simultaneous outputs of different filter functions. The second structure has a single voltage output and single voltage input distributed to different circuit nodes for a universal realization. The authors not only propose such filter structures, but also show how analytical synthesis can be used to produce filter circuits that have less active elements than those recently reported voltage-mode structures which are based on differential-input OTAs. This represents another attractive feature from chip area, and power consumption point of view. Simulation results verifying the theoretical analysis of the proposed filter structure are included.     

电流模式高阶OTA-C高通滤波器的设计

提出了一种新的电流模式高阶OTA—C高通滤波器的设计方法。由该方法导出的滤波器具有最少的元件．n阶滤波器仅需n个OTAs和n个电容，所有的电容均接地，便于集成且与VLSI工艺兼容。文中给出了6阶滤波器设计实例，PSPICE仿真结果与理论分析相吻合，验证了该设计方法的可行性。     

Design of a new low power MISO multi-mode universal biquad OTA-C filter

ABSTRACT

In this article, a new low-power multiple-input, single-output (MISO) multi-mode universal biquad operational transconductance amplifier-capacitor (OTA-C) filter with a minimum number of active and passive components is proposed. The proposed filter employs three OTAs, one inverter and two grounded capacitors. The proposed filter can realise all filter frequency responses including low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) in all operation modes including voltage, current, tranasresistance and transconductance modes using the same topology. Furthermore, sensitivity analysis is done which shows that the proposed filter has a low sensitivity to the values of the active and passive elements. The proposed filter is simulated in HSPICE using 0.18 µm CMOS technology. The HSPICE simulation results demonstrate that the proposed filter consumes only 35 μW at 2.5 MHz from a ±0.5 V supply voltage, while all of the transistors are biased in strong inversion region. Also, the simulation results are in a close agreement with the theoretical analysis which is done in MATLAB. Furthermore, the process, voltage and temperature variation simulations are done to study the effect of non-idealities on the performance of the proposed filter. It is shown that the simulation results justify a 4.8%, 0.8% and 20% variations of the centre frequency for process, voltage and temperature, respectively. Finally, Monte-Carlo, noise and transient simulations are done to justify the good performance of the proposed filter performance.     

OTA-C biquad-based filter silicon compiler

An integrated software system that facilitates the design, and integrated-circuit layout of continuous-time OTA-C filter biaquad-based structures with typical cutoff frequenceis for a 3µm technology in the 500 kHz-8 MHz range is described. The proposed integrated software system consists of three separate software modules written in the C language for the Apollo workstation (DN3000). The first module is a general filter approximation package. This program can approximate conventional magnitude, arbitrary magnitude, arbitrary group delay equalizer, arbitrary magnitude with group delay specifications. The second module aides in the synthesis of the biquad-based OTA-C filter structures. This module is unique in that the C code has the rule-based language CLIPS embedded within the code, and takes into account OTA-C filter nonidealities. An expert system using CLIPS was developed to select an appropriate OTA-C filter structure based on the nonidealities of the structures. After the filter structure has been chosen, the program will guide the user in the calculation of the capacitor values. These calculations are based on the nonidealities of the OTAs included in the standard cell library for layout, in addition the design of special purpose OTA as another alternative is also considered. Furthermore, the program will develop the necessary input files for the layout generator. The final module is a modified version of AIDE2, a standard cell layout generator for switched-capacitor circuits. The input files to the modified AIDE2 is a C language program that describes the circuit (i.e., standard cells and their netlist). The output file is a CALTECH Intermediate Format (CIF) file that is required for fabrication.1. The first version of FIESTA [22] was written in basic for personal computers and it is a primitive (and reduced) version of the second version here discussed.2. Not yet implemented in current version of FIESTA.3. In figure 3 the input currentsI _{in 1},I _{in 2},I _{in 3} can be implemented using OTAs.4. The OTA-C filter can be tuned using the tail currents of the OTAs. Therefore, the capacitors do not need to be any exact value.     

Current-Mode Delay Equalizer Design Using Multiple Output OTAs

Two new current-mode allpass sections based on dual-output OTAs (DO-OTAs) and triple-output OTAs (TO-OTAs) and grounded capacitors are described. Techniques to minimize the equalizer active device count and efficiently simulate grounded resistors are proposed. A fifth-order group delay equalizer based on the presented allpass sections is designed and simulated using multiple-output CMOS OTAs. Numerical optimization is used to determine the equalizer order and parameters. SPICE simulation results are given, demonstrating that the equalizer can effectively compensate the delay characteristic of a fourth-order 4 MHz lowpass Chebyshev filter to 8 ns ripple over 90% of the filter passband.     

Novel multiple function analog filter structures and a dual-mode multifunction filter

This paper reports three multi-function filters each of which realizes at least three basic functions without any external passive elements. Depending on the circuit, from one to four operational transconductance amplifiers (OTAs), and two operational amplifiers (OPAMPs) are employed. All three circuits are transimpedance-mode circuits; one of them can also operate as a current-mode filter. Therefore this filter represents a dual-mode, multifunction filter. The presented theory is verified with macro models in simulation program with integrated circuit emphasis (SPICE) simulations and post layout simulations, which are carried out with parasitics extracted from the layouts of the filter chips.     

开关电源输入EMI滤波器设计与仿真

开关电源中常用EMI滤波器抑制共模干扰和差模干扰。三端电容器在抑制开关电源高频干扰方面有良好性能。文中在开关电源一般性能EMI滤波器电路结构基础上,给出了使用三端电容器抑制高频噪声的滤波器结构。并使用PSpice软件对插入损耗进行仿真,给出了仿真结果。     

Analytical Synthesis of Current-Mode High-Order Single-Ended-Input OTA and Equal-Capacitor Elliptic Filter Structures With the Minimum Number of Components

None of the previously reported third-order and fourth-order operational transconductance amplifier and capacitor (OTA-C) elliptic filter structures use the minimum number of active and passive components. After an innovative algebraic decomposition for a complicated transfer function, i.e., a new analytical synthesis method, a current-mode odd-nth-order and a current-mode even-nth-order OTA-C elliptic filter structure having the following advantages are presented: 1) all the OTAs have single-ended inputs; 2) all the capacitors are grounded; 3) the minimum active and passive components are used. An equal-capacitance-type structure is designed taking into account the difficulty of precisely fabricating capacitances in integrated circuits. Although the above three advantages lead to the lowest total parasitics and to the most precise output response, the small deviations (such as the 3.5159% error in f_p) of the four parameters of the new third-order OTA-C elliptic filter can be drastically reduced (for example, to 0.1553% error in f_p) by only slightly tuning the four transconductances, but fixing the ratio of the given three capacitances, and without adding any other active and passive components. H-spice high-pass and low-pass simulations with 0.35-mum process are provided to demonstrate the theoretical results.     

电流模式n阶传输函数的OA-OTA实现

提出了一种新的实现任意 n阶电流模式传输函数的网络结构。该电路仅含运算放大器 (OA)和运算跨导放大器 (OTA)有源器件 ,因而适于全集成。适当设置 OTA的跨导值能实现任意高阶传输函数 ,且传输函数的系数可独立调整。文中推导了滤波器的设计公式 ,并给出了截止频率为 1 0 0 k Hz的三阶巴特沃斯低通滤波器实例 ,PSPICE仿真结果表明所提电路及设计公式是正确的     

Novel voltage-mode biquad without external passive elements

This paper introduces a voltage-mode biquad filter using only active devices such as operational amplifiers and operational transconductance amplifiers (OTAs). The circuit configuration is obtained from Soderstrand's active-R state variable filter as a prototype. The proposed circuit can realize five different biquad transfer functions, and the circuit characteristics can be electronically tuned by adjusting the transconductance gains of the OTAs. An example is given, together with simulated results by PSPICE. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.     

Universal three input and one output current-mode filter withoutexternal passive elements

A new current-mode universal filter is proposed. The filter uses only operational amplifiers and operational transconductance amplifiers (OTAs) and can realise lowpass, highpass, bandpass, notch and allpass responses without changing circuit topology. The parameters ω₀, ω₀/Q₀, and the gain can be electronically tuned by adjusting the bias currents of the OTAs. The proposed circuit has low sensitivity     

Electronically tunable voltage-mode universal filter with single-input five-output using simple OTAs

This article presents a new electronically tunable voltage-mode universal biquadratic filter with single-input five-output using simple operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed configuration provides low-pass, band-pass, high-pass, band-stop and all-pass voltage responses at a high-impedance input terminal that enables easy cascading in voltage-mode. The natural frequency and the quality factor can be set orthogonally by adjusting the circuit components. The natural frequency can also be controlled electronically by adjusting the bias currents of the OTAs. For realising all the five standard filtering functions, no critical-matching conditions are imposed and all the incremental parameter sensitivities are low. Experimental and simulation results that confirm the theoretical predictions are given.     

Design of transimpedance low-pass filters

The input of a transimpedance filter is a current signal, while its output is a voltage signal. In this article, a design method for a transimpedance filter is introduced. Also, the topologies and calculation methods of the parameters of three biquadratic transimpedance low-pass (LP) filter circuits are presented in detail, according to the value of Q which is low or medium or high. As for the high-order filter, it can be designed by transimpedance LP biquad section as first stage cascaded with voltage-mode LP filters. Finally, to verify the effectiveness of the design, a design example of a high-order transimpedance LP filter is given.     

用四端子器件实现的一种新型直接序列扩频匹配滤波器

提出了用四端子器件实现一种新型结构的直接序列扩频匹配滤波器，根据四端子器件的特点，从结构上分析了新型匹配滤波器结构相对于传统的数字匹配滤波器结构的优越性所在，它既保留了传统数字匹配滤波器的低功耗等特点，同时又具有结构简单的特点，大大减少了器件数目，HSPICE的模拟结果及测试芯片的实验结果验证了系统结构设计的可行性。     

Current-mode elliptic filter design based on symmetrical current switching

This paper describes a current-mode elliptic filter structure based on dual-output OTAs and grounded capacitors. The filter is capable of producing both lowpass and highpass notch responses without changing the filter structure. This is achieved using a symmetrical current switching technique based on two switches controlled with a 2-bit digital word. The proposed filter structure forms a basic second-order building block in the design of high-order elliptic filters with tuneable frequency response. To confirm the theoretical analysis, simulated and measured results of fourth-order elliptic lowpass and highpass filters with tuneable bandwidth in the range of 0.65MHz to 1.3MHz are included. Finally, detailed analysis of the OTAs non-ideal parameters on the filter performance is presented and an example is given.     

多元一维光子晶体滤波器的研究

介绍了一种形式如(ABBA)m(ABBB)m的新型二元特殊复周期结构光子晶体来近似分析研究多元一维光子晶体的滤波特性,并运用光学导纳特征矩阵方法数值分析了这种结构以及它的一种掺杂形式(ABBA)mCn(ABBB)m结构光子晶体的能带特性.研究结果表明,这种新结构的光子晶体的禁带宽度较之几种常见二元结构很大或多出一个大的带隙区,非常适合应用于宽带滤波器;同时在某些频率段出现的透过峰也适合应用于多通道窄带滤波器,在引入掺杂C时,发现C的材料,厚度可以影响窄透过峰的位置及多少,对多通道窄带滤波器的设计也很有帮助.而在使用多种材质进行替代研究后发现,多样化的介电常数对光子晶体的禁带宽度及透过峰的宽窄,位置有一定影响.由于其参数设计简单,很适用于设计不同种类要求的滤波器.     

New voltage-mode universal filter and sinusoidal oscillator using only single DBTA

In this article, a new voltage-mode second-order universal frequency filter and sinusoidal oscillator using only single differential-input buffered and transconductance amplifier (DBTA) is presented. The proposed voltage-mode filter structure using single DBTA and four passive elements can provide all standard filter functions, i.e. low-, band-, high-pass, band-stop, and all-pass without changing the circuit topology and enables independent control of the quality factor Q using single passive element. The circuit requires the minimal number of active and passive elements with no conditions for component matching. By slight modification of the proposed filter structure, the new DBTA-based sinusoidal oscillator is easily obtained. The oscillation condition and the oscillation frequency are independently adjustable by different virtually grounded passive elements. The proposed sinusoidal oscillator employs only grounded capacitors. The passive and active sensitivities of all the proposed circuit configurations are low. PSPICE simulations using a BJT realisation of DBTA and experimental results based on commercially available amplifiers OPA860 and MAX436 are included, which prove the workability of the proposed circuits.