基于单个CDCTA的低压电控调谐电流模式多相位正弦振荡器的设计

提出了一种全新的电流模式多相位正弦振荡器电路。该电路仅使用一个电流差分级联跨导放大器(CDCTA)和接地无源元件,能产生n(n为奇或偶)个等相位差的电流信号,电路结构简单、工作电压低、输出阻抗高、振荡频率高,而且振荡条件和振荡频率独立可调。计算机CADENCE软件仿真和流片测试结果验证了理论分析的正确性。     

一种CMOS电流控制振荡器的分析与设计

提出了一种结构简单的CMOS电流控制模式振荡器.该电路充分利用系统内部基准电流源产生的电流信号对电容进行充放电,在5 V电源电压下,经过控制电路作用后,上升时间和下降时间非常小,使产生的输出振荡波形更接近理想矩形波;通过调节基准源电流信号或者电路中电容值的大小,可以调节振荡输出波形的频率和占空比.     

一种低功耗宽频率调谐范围的伪差分环形VCO

设计了一种低功耗、宽频率调谐范围的伪差分环形压控振荡器(VCO).电路设计分为振荡环路设计和电流源设计两部分.在振荡器的振荡环路部分,提出了一种新颖的降低功耗的方法,即通过动态地调节接入振荡环路的锁存器,减小驱动电流,降低功耗;在振荡器的控制电源部分,采用gain-boost结构,设计了一款理想的可控双电流源,实现了振荡器的宽频率调谐范围.基于SMIC 65 nm工艺,在1.8V工作电压下,对振荡器进行了后仿验证.结果表明,在频率为900 MHz时,振荡器的功耗仅为3.564 mW;当控制电压在0.6～1.8 V变化时,振荡器的频率调谐范围可宽达0.495 ～1.499 GHz.     

一种基于CCⅡ＋和接地RC的新型振荡器

提出了由一个同相第二代电流传输器，两个接地电容器和两个接地电阻构成的正弦振荡器，运用负振荡器方法分析了该电路，得出了振荡条件和振荡频率，给出了电路的实验结果。该电路结构简单，且无源元件全部接地，便于集成。     

基于电流模式施密特触发器的CCCⅡ±张弛振荡器

提出了一种基于电流模式施密特触发器的CCCⅡ±张弛振荡器.该电路的振荡信号周期可由接地电容线性改变,而频率则与CCCⅡ±的偏置电流成正比,PSPICE仿真结果与理论分析相符.     

CCCDTA的零-镜实现及其对正交振荡器综合的应用

为综合基于CCCDTA的正交振荡器,根据CCCDTA的端口关系,首次提出了CCCDTA的4个零-镜描述。借助已报道振荡器的NAME方程及其8个零-镜描述,实现2个基于CCCDTA的正交振荡器。通过调节2个CCCDTA的偏置电流,还能电控电路的振荡条件和振荡频率。作为一个例子,当振荡条件满足(IB2>IB1=260μA)时,实现了一个振荡频率为79.62 kHz的正交振荡器。计算机仿真证明所综合的电路正确有效。     

用改进的非线性电流源法分析微波振荡器的稳态响应

本文提出用改进的非线性电流源法和振荡器的振荡条件相结合,进行微波FET振荡器非线性分析的方法.非线性电流源法已经被证明为分析微波振荡器的一种行之有效的方法.但是,当电路中含有多维非线性元件时(例如FET中的I_(d5)(V_(g5),V_(d5)),以往的非线性电流源法就显得无能为力.在此,我们将对非线性电流源法进行改进,并将它运用到微波FET振荡器的非线性分析中.改进的非线性电流源法能够有效地处理含有多维非线性元件电路的分析问题,从而大大提高了非线性电流源法的分析能力和实用性,扩大了其应用范围.     

基于CDCTA的双模式等幅正交振荡器

针对正交振荡器实现复杂、振幅不相等、模式单一等问题,提出了一种基于电流差分级联跨导放大器的双模式正交振荡器。该电路仅使用一个电流差分级联跨导放大器、一个接地电阻和两个接地电容,可以同时产生等幅电压和电流正交信号。电路结构简单,灵敏度低,易于集成,振荡条件和振荡频率可相互独立地电控调谐。PSPICE仿真与硬件实验结果验证了理论分析的正确性。     

单片CDCTA-C低功耗电控调谐双模式三阶正交振荡器的设计

针对振荡器功耗大和振荡频率低的问题,提出了一种基于电流差分级联跨导放大器的三阶正交振荡电路.该电路仅使用一个电流差分级联跨导放大器和三个接地无源电容,可以同时产生两组等幅正交电流信号和一组等幅正交电压信号.电路结构简单,功耗低至1.8mW,最大灵敏度绝对值仅0.5,振荡频率可达10MHz数量级,而且振荡条件和震荡频率可相互独立地电控调谐.计算机模拟和流片芯片测试结果验证了理论分析的正确性.     

一种基于0.5 μm CMOS工艺的补偿型电流控制振荡器设计

提出了一种基于比较器的CMOS电流控制振荡器电路,该振荡器采用偏置电流对电容充放电,产生精准锯齿波,比较器及后续电路产生时序方波作为比较器输入,从而产生周期振荡.自偏置电路利用电阻和PNP管相反的温度系数产生PTAT、NTAT两路电流,叠加得到一路与温度无关的基准电流、实现了温度补偿;高摆幅共源共栅电流镜结构具有高PSRR实现了电源电压补偿.本设计采用0.5 μmCMOS工艺,典型情况下,振荡器频率为1.224 MHz,占空比为50%,通过spectre仿真结果表明:该振荡器在3.3 V～5 V的工作电压下、-40～120℃温度范围内都具有较好的工作频率.     

RC移相式振荡器振荡频率计算

RC移相式正弦波振荡器是一种常用的低频振荡器.文章基于电路发生正弦波振荡的平衡条件,推导出了电路的振荡频率和晶体管电流放大倍数的约束条件,分析方法和结论对于分析和使用该电路都有一定的参考价值.     

An AGC Circuit Design for a Variable-Frequency Sinusoidal Oscillator with Wide Frequency Range and Low Distortion Level

An up-down counter, multiplier, digital-to-analog (D/A) converter, and high-speed comparators are employed to achieve an automatic gain control (AGC) circuit, which corrects the pair of characteristic roots of the overall system automatically to the imaginary axis of the complex frequency plane. A negative feedback technique with digital hardware is applied on the loop gain control. No lowpass filter is needed to detect the oscillation amplitude. Thus, this technique is suitable for sinusoidal oscillators with a wide oscillation frequency range. Wien-bridge and phase-shift oscillators with an oscillation frequency range from 17 Hz to 1 MHz are tested with the proposed AGC circuit. The total harmonic distortions of the Wien-bridge sinusoidal oscillator with the proposed AGC circuit are verified to be very small. An application to a variable-frequency sinusoidal oscillator is also described. The experimental results demonstrate the static characteristics and dynamic responses of the overall system.     

Reply to comment on “Identification of a class of two CFOA-based sinusoidal RC oscillators”

This reply relates to a recently published comment (Wangenheim, Analog Integrated Circuits and Signal Processing 67:117–119, 2011) which discusses the validity of the well known Barkhausen criterion of sinusoidal oscillation. According to the author failure to produce sinusoidal oscillation if real amplifiers are used cannot be described as “failure of the Barkhausen criterion”. This conclusion was reached based on the SPICE simulation of a CFOA-based oscillator circuit. It is shown here that while this result can support the verbal formulation of the Barkhausen criterion, it can not support its widely used mathematical formulation and the results obtained based on it. In fact this widely used mathematical formulation of the Barkhausen criterion can not predict the exact frequency and condition of oscillation of any sinusoidal oscillator circuit.     

A novel variable frequency sinusoidal oscillator using a single current conveyor

A new active RC second-order sinusoidal oscillator using a single second generation current conveyor is described. A single grounded resistor adjusts the circuit for oscillation and a single grounded capacitor controls the oscillation frequency without affecting the oscilllation condition.     

Four new oscillators using operational transresistance amplifier

In this paper, four new sinusoidal waveform generators based on the operational transresistance amplifier (OTRA) are presented. The first proposed circuit is a minimum component RC sinusoidal oscillator circuit with one OTRA and a few passive components. The second and third proposed circuits consist of one OTRA and a few passive components, among them two passive components are connected to ground. These circuits are able to control the condition of oscillation and frequency of oscillation independently. The fourth proposed quadrature oscillator circuit uses two OTRAs as main active building blocks and a few external passive components to generate the oscillations. The IC AD844AN is adopted to implement the proposed circuits on a laboratory breadboard with external passive components. Both the SPICE simulation and experimental results are given to verify the theoretical analysis of the proposed circuits.     

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.     

Current‐mode quadrature oscillator using current differencing transconductance amplifiers

This article presents a new electronically tunable single‐element‐controlled current‐mode quadrature sinusoidal oscillator circuit using current differencing transconductance amplifiers (CDTAs). The proposed oscillator is consisted of two CDTAs, two grounded capacitors and one grounded resistor, which is beneficial to monolithic integrated circuit implementation both in CMOS and bipolar technologies. The condition of oscillation and the frequency of oscillation are independently controllable. The frequency of oscillation can also be electronically controlled by adjusting the bias current of CDTA. The circuit provides four quadrature current outputs and two quadrature voltage outputs. The current output terminals possess high impedance level. PSPICE simulation results are used to verify the performance of the proposed circuit implemented at the transistor level. The measurement results support the computer simulations.     

A general method to predict the amplitude of oscillation in nearly sinusoidal oscillators

In this paper, a general methodology for predicting the amplitude of oscillation in nearly sinusoidal oscillators is presented. The method relies on the recently proposed projection technique for the computation of the center manifold and on the Hopf normal form theory to approximate the corresponding limit cycle in state space. The Colpitts oscillator is selected as a case study and, for this circuit, a closed-form expression for the amplitude of oscillation is derived as a function of the circuit parameters.     

New Rc-Active oscillator configuration employing unity-gain amplifiers

A new sinusoidal oscillator configuration is proposed which employs op-amps as unity-gain amplifiers. The proposed circuit offers independent single-element controls for adjusting the condition of oscillation and oscillation frequency and has very good frequency stability. Practically, the circuit works well over a frequency range much higher than possible with other known types of oscillators (which use op-amps as ±K-gain or infinite-gain VCVSs). The proposed configuration also provides useful prototypes to derive novel switched-capacitor oscillators.