CDTA-based electronically tunable current-mode quadrature oscillator

This paper presents two new current differencing transconductance amplifiers (CDTAs)-based electronically tunable current-mode four-phase quadrature oscillators (QO). The proposed QOs consist of two CDTAs, one resistor and two grounded capacitors, respectively, which are suitable for monolithic integration. The condition of oscillation (CO) and frequency of oscillation (FO) can be independently controlled, and the FO can be electronically tunable by adjusting the bias current of the CDTA. Moreover, the QOs can provide four quadrature output currents at high-output-impedance nodes, which enable the QOs can be connected directly to the next stage without any impedance matching requirements. Cadence IC Design Tools 5.1.41 (Cadence Design Systems Inc., San Jose, CA) post-layout simulation results and experimental evidence are included to confirm the theory.     

Realization of electronically tunable voltage-mode/current-mode quadrature sinusoidal oscillator using ZC-CG-CDBA

This paper presents a first of its kind canonic realization of active RC (ARC) sinusoidal oscillator with non-interactive/independent tuning laws, which simultaneously provides buffered quadrature voltage outputs and explicit quadrature current outputs. The proposed circuit is created using a new active building block, namely the Z-copy controlled-gain current differencing buffered amplifier (ZC-CG-CDBA). The circuit uses three resistors and two grounded capacitors, and provides independent/non-interactive control of the condition of oscillation (CO) and the frequency of oscillation (FO) by means of different resistors. Other advantageous features of the circuit are the inherent electronic tunability of the FO via controlling current gains of the active elements and the suitability to be employed as a low-frequency oscillator. A non-ideal analysis of the circuit is carried out and experimental results verifying the workability of the proposed circuit are included.     

Electronically tunable current-mode square-root-domain first-order multifunction filter

In this article, a new current-mode square-root-domain first-order multifunction filter is designed. The filter circuit has a very simple structure; it uses only the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and a grounded capacitor. All transistors’ aspect ratios are the same. It provides lowpass, highpass and allpass responses simultaneously for a single input signal. It can be electronically tuned by changing an external DC current. The filter operates with a single supply voltage of 2.5 V. The proposed circuit has been simulated with PSPICE electronics circuit simulation program (Cadence OrCAD Capture CIS Version 9.2) simulation programs using TSMC 0.35 μm (Taiwan Semiconductor Manufacturing Company) Complementary Metal-Oxide-Semiconductor (CMOS) process parameters.     

Single-resistance-controlled quadrature oscillator using current differencing buffered amplifiers

A single-resistance-controlled quadrature oscillator circuit using current differencing buffered amplifiers (CDBAs) as active components is proposed. The proposed circuit is realised through the employment of two CDBAs, three resistors and two grounded capacitors. Outputs of two sinusoidal with 90° phase difference are available. The oscillation condition and the oscillation frequency of the proposed quadrature oscillator can be controlled independently by a single resistor. In comparison with the previously reported circuits, the proposed configuration considerably reduces the number of passive elements.     

Electronically tunable current-mode biquadratic filter and four-phase quadrature oscillator

This paper presents a current-mode biquadratic filter based on ZC-CFTAs. It employs only three ZC-CFTAs, one resistor and two grounded capacitors. It can simultaneously realize not only highpass and lowpass filtering functions but also two different forms of bandpass ones; one has a pass-band gain of Q, the other, a pass-band gain of unity. Its ω_o and Q can be tuned orthogonally through adjusting bias currents of ZC-CFTAs. Moreover, the proposed circuit can also be modified to be a current controlled four-phase quadrature oscillator with small distortion. Non-ideal analysis and sensitivity analysis are provided. The results of circuit simulations are in agreement with theory.     

New electronically tunable current-mode universal biquad filter using translinear current conveyors

In this study, a new electronically tunable current-mode universal filter with two inputs and two outputs employing one translinear current conveyor, one translinear current conveyor with controlled current gain and two grounded capacitors is presented. The proposed circuit offers the following attractive features: realisation of low-pass, band-pass, high-pass, band-stop and all-pass current responses from the same configuration; employment of the minimum active and passive components; no requirement of component matching conditions; independent current-control of the parameters natural frequency (ω_o) and quality factor (Q); low active and passive sensitivities; and high impedance output. The characteristics of the proposed circuit are simulated using PSPICE to confirm the theory.     

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。     

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.     

Electronically tunable sinusoidal oscillator circuit with current and voltage outputs

A new circuit configuration for the realisation of an electronically tunable sinusoidal oscillator is presented. The proposed circuit uses only one current backward transconductance amplifier (CBTA), two grounded capacitors and one resistor. Using current controlled CBTA (CC-CBTA) instead of the CBTA, the resistor can be completely removed. It has also current-mode (CM) and voltage-mode (VM) outputs, simultaneously. The workability of the proposed structure has been demonstrated by both simulation and experimental results.     

A novel current-mode multiphase sinusoidal oscillator using MO-CDTAs

This article presents a novel current-mode multiphase sinusoidal oscillator. The oscillator can produce two groups of n output currents and one group of 2n output currents (n being even or odd) with equal amplitude and equal-phase space. The circuit only uses one multi-output current differencing transconductance amplifier and one grounded capacitor for each section, and is easy to integrate. Its oscillation condition and frequency can be electronically tuned linearly and independently, and its outputs possess high impedance. It is important that the multi-frequency oscillation in the oscillator is studied and a method for eliminating unnecessary oscillation is given. In addition, the inverting amplifier with the automatic gain control is employed to reduce the distortion of output signals. Finally, the frequency error is analysed and the simulated results are illustrated.     

SITO electronically tunable high output impedance current-mode universal filter

A novel current-mode (CM) single-input and three-output (SITO) universal filter using two second generation current controlled conveyors (CCCIIs), one current follower (CF) and two capacitors is presented. The circuit is fully programmable and implements all the five generic filtering functions. The lowpass (LP), bandpass (BP), and highpass (HP) functions can be realized simultaneously while Notch (BS) and allpass (AP) responses can be implemented simply by connecting the appropriate node currents without requiring additional elements. The availability of currents at high impedances, facilitate cascadibility feature. The filter performance factors ω₀ and ω₀/Q are electronically tunable through separate bias currents of the CCCIIs. SPICE simulation results are included to confirm the workability of the proposed circuit.     

First CFOA-based explicit-current-output quadrature sinusoidal oscillators using grounded capacitors

To date, no current-feedback operational amplifier (CFOA)-based sinusoidal oscillator has been reported which provides all the following features simultaneously: (i) current-mode quadrature sinusoidal oscillator providing two explicit-current-outputs (ECOs) from high output impedance terminals, (ii) employing no more than three CFOA ICs and six passive components, which include two grounded capacitors, (iii) offers independent tuning of the condition of oscillation (CO) via a resistor and (iv) provides tunability of the ratio of amplitudes of the generated quadrature ECOs via a separate resistor. To the best of authors' knowledge, this article reports first CFOA-based QOs in current-mode (i.e. providing two ECO signals). Experimental results using AD844 CFOA ICs from Analog Devices have been included to verify the workability of the proposed oscillator circuits. An example automatic gain control (AGC) loop to regulate the oscillation amplitude and control the THD has also been used and verified using SPICE simulations using the AD844 macro-model.     

Compact VDTA-based current-mode electronically tunable universal filters using grounded capacitors

This paper presents a compact current-mode three-input single-output (TISO) type universal filter. Only one voltage differencing transconductance amplifier (VDTA) and two grounded capacitors are employed in the proposed filter. The circuit can realize lowpass, bandpass, highpass, bandstop and allpass biquadratic filter outputs by connecting the appropriate inputs, and offers electronic control of the natural angular frequency (ω₀) and quality factor (Q) by means of adjusting the transconductance gain of the VDTA. In addition, by slight modification of the proposed scheme, another more useful TISO construction with orthogonal ω₀–Q tuning has been obtained. Both the discussed universal filters have been shown to have low incremental active and passive sensitivities. To demonstrate the performances of the filters and verify the theoretical analysis, computer simulations are accomplished with the PSPICE program.     

Quadrature oscillator using CCCCTAs and grounded capacitors with amplitude controllability

The realisation of two electronically tunable current-mode quadrature oscillators using Current Controlled Current Conveyor Tranconductance Amplifiers (CCCCTAs) and grounded capacitors is presented. The proposed circuits offer the following advantages. The condition of oscillation and the frequency of oscillation can be orthogonally controlled. Availability of electronic control of amplitude of output current is achieved. The oscillators have high outputs impedance which facilitates easy driving an external load without additional current buffers. The proposed circuits are constructed by using two active elements and all grounded capacitors which are attractive for integration and have low active and passive sensitivities. The PSPICE simulation and experimental results are included to show the workability of the proposed circuit.     

Resistorless dual-mode quadrature sinusoidal oscillator using a single active building block

This paper presents a new realization of resistorless mixed-mode (i.e. both voltage-mode and current-mode) quadrature sinusoidal oscillator using a new active building block (ABB) called the differential voltage current-controlled conveyor transconductance amplifier (DVCCCTA). The proposed oscillator circuit uses a single DVCCCTA, two grounded capacitors (GCs) and does not employ any external linear resistors. The tuning laws for the condition of oscillation (CO) and the frequency of oscillation (FO) are non-interactive; and controlled by separate bias currents. The circuit provides two explicit quadrature current outputs and two quadrature voltage outputs and thus can be classified as a mixed-mode quadrature oscillator. Another notable feature of the proposed circuit is that it can also be used as a biquadratic filter to realize low-pass and band-pass filtering functions simultaneously. Non-ideal analysis of the circuit is provided and PSpice simulation results have been included to verify the workability of the proposed circuit.     

基于MO-CCCDTA的电控调谐电流模式六阶椭圆带通滤波器

提出了一个多输出电流差分跨导放大器(MO-CCCDTA),利用它设计了一个电流模式二阶带通、二阶高通带阻和二阶低通带阻电路,以此为基础,利用级联法设计了电流模式六阶椭圆带通滤波器.该滤波器仅使用3个MO-CCCDTA、1个CDTA和7个电容,通过调节偏置电流,各滤波器参数均能被电控调谐.计算机仿真表明电路正确有效.     

CMOS-based active RC sinusoidal oscillator with four-phase quadrature outputs and single-resistance-controlled (SRC) tuning laws

This paper proposes a very compact CMOS realization of active RC sinusoidal oscillator capable of generating four quadrature voltage outputs. The oscillator is based on the cascade of lossless and lossy integrators in loop. The governing laws for the condition of oscillation (CO) and the frequency of oscillation (FO) are single-resistance-controlled (SRC) and which allow independent FO tuning. Unlike previously reported SRC-based sinusoidal oscillators based on the active building block (ABB) based approach and which aim at reducing the number of employed ABBs, this direct CMOS realization provides a much reduced transistor count circuit and consequently offers a low power solution. A comparison with previously reported SRC oscillators in terms of number of transistors and current consumption has been provided. As a design example, a 160.2 kHz oscillator (typical process, T = 27 °C) with 82 μW power consumption is designed in 65 nm CMOS technology with supply voltage of ±0.5 V.     

Electronically tunable mutually coupled circuit using only two active components

A new circuit for realisation of the mutually coupled circuit, which is also called the synthetic transformer, is proposed. The proposed circuit uses two current controlled current conveyor transconductance amplifiers (CC-CCTAs), one grounded resistor and two grounded capacitors. The primary self-inductance, the secondary self-inductance and the mutual inductance can be independently controlled and can be tuned electronically by changing the biasing current of the CC-CCTAs. It uses two grounded capacitors which are suitable from the point of integrated circuit implementation. It has a good sensitivity performance with respect to tracking errors and passive components. The validity of the proposed circuit is demonstrated by PSpice simulations.     

A low-power, high-frequency, all-NMOS all-current-mirror sinusoidal quadrature oscillator

A low-power, high-frequency, sinusoidal quadrature oscillator is presented through the use of only current mirrors where the small-signal paths are realized through all NMOS transistors. The technique is relatively simple based on (i) inherent time constant of current mirrors, i.e. the internal capacitances and the transconductance of a diode-connected NMOS, (ii) a negative resistance formed by a transconductance of a diode-connected NMOS load of a current mirror. No external passive components are required. As a particular example, a 2.83 GHz, 0.374 f_T, 0.38 mW sinusoidal quadrature oscillator is demonstrated. Total harmonic distortions are less than 0.8%. The oscillation frequency is current-tunable over a range of 640 MHz or 22.62%. The amplitude matching and the quadrature phase matching are better than 0.04 dB and 0.17°, respectively. A figure of merit called a normalized carrier-to-noise ratio is 158.23 dBc/Hz at the 2 MHz offset from 2.83 GHz. Comparisons to other approaches are also presented.     

An improved universal CMOS current-mode analogue function synthesiser

A CMOS integratable current-mode analogue function synthesiser circuit is presented. The proposed circuit is based on approximating the required function using its sixth-order Taylor series expansion. These approximations can be implemented by adding the weighted output currents of a number of basic building blocks, built around a basic current squarer, and a constant current. The proposed circuit can simultaneously realise 32 different mathematical functions and can be easily expanded to accommodate many others. SPICE and Monte Carlo simulation results demonstrating the circuit performance are included.