4,134 research outputs found

    Study of Adjustable Gains for Control of Oscillation Frequency and Oscillation Condition in 3R-2C Oscillator

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    An idea of adjustable gain in order to obtain controllable features is very useful for design of tuneable oscillators. Several active elements with adjustable properties (current and voltage gain) are discussed in this paper. Three modified oscillator conceptions that are quite simple, directly electronically adjustable, providing independent control of oscillation condition and frequency were designed. Positive and negative aspects of presented method of control are discussed. Expected assumptions of adjustability are verified experimentally on one of the presented solution

    On the Design of Voltage-Controlled Sinusoidal Oscillators Using OTA's

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    A unified systematic approach to the design of voltage-controlled oscillators using only operational transconductance amplifiers (OTA's) and capacitors is discussed in this paper. Two classical oscillator models, i.e., quadrature and bandpass-based, are employed to generate several oscillator structures. They are very appropriate for silicon monolithic implementations. The resulting oscillation frequencies are proportional to the transconductance of the OTA and this makes the reported structures well-suited for building voltage controlled oscillators (VCO's). Amplitude stabilization circuits using both automatic gain control (AGC) mechanisms and limitation schemes are presented which are compatible with the transconductance amplifier capacitor oscillator (TACO). Experimental results from bipolar breadboard and CMOS IC prototypes are included showing good potential of OTA-based oscillators for high frequency VCO operation.ComisiĂłn Interministerial de Ciencia y TecnologĂ­a ME87-000

    CMOS OTA-C high-frequency sinusoidal oscillators

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    Several topology families are given to implement practical CMOS sinusoidal oscillators by using operational transconductance amplifier-capacitor (OTA-C) techniques. Design techniques are proposed taking into account the CMOS OTA's dominant nonidealities. Building blocks are presented for amplitude control, both by automatic gain control (AGC) schemes and by limitation schemes. Experimental results from 3- and 2- mu m CMOS (MOSIS) prototypes that exhibit oscillation frequencies of up to 69 MHz are obtained. The amplitudes can be adjusted between 1 V peak to peak and 100 mV peak to peak. Total harmonic distortions from 2.8% down to 0.2% have been measured experimentally.ComisiĂłn Interministerial de Ciencia y TecnologĂ­a ME87-000

    Very high frequency CMOS OTA-C quadrature oscillators

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    An approach to the design of high-frequency monolithic voltage-controlled oscillators using operational transconductance amplifiers and capacitors is given. Results from two 3 ÎŒm CMOS prototypes are presented. Both frequency and amplitude of the oscillations can be tuned by means of control voltages. Programmable oscillator frequencies up to 56.1 MHz are obtained, and the amplitudes are adjustable between 1 V peak-to-peak and 100 mV peak-to-peak. Total harmonic distortions from 2.8% down to 0.2% were experimentally measured

    A wideband linear tunable CDTA and its application in field programmable analogue array

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    This document is the Accepted Manuscript version of the following article: Hu, Z., Wang, C., Sun, J. et al. ‘A wideband linear tunable CDTA and its application in field programmable analogue array’, Analog Integrated Circuits and Signal Processing, Vol. 88 (3): 465-483, September 2016. Under embargo. Embargo end date: 6 June 2017. The final publication is available at Springer via https://link.springer.com/article/10.1007%2Fs10470-016-0772-7 © Springer Science+Business Media New York 2016In this paper, a NMOS-based wideband low power and linear tunable transconductance current differencing transconductance amplifier (CDTA) is presented. Based on the NMOS CDTA, a novel simple and easily reconfigurable configurable analogue block (CAB) is designed. Moreover, using the novel CAB, a simple and versatile butterfly-shaped FPAA structure is introduced. The FPAA consists of six identical CABs, and it could realize six order current-mode low pass filter, second order current-mode universal filter, current-mode quadrature oscillator, current-mode multi-phase oscillator and current-mode multiplier for analog signal processing. The Cadence IC Design Tools 5.1.41 post-layout simulation and measurement results are included to confirm the theory.Peer reviewedFinal Accepted Versio

    Novel active function blocks and their applications in frequency filters and quadrature oscillators

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    KmitočtovĂ© filtry a sinusoidnĂ­ oscilĂĄtory jsou lineĂĄrnĂ­ elektronickĂ© obvody, kterĂ© jsou pouĆŸĂ­vĂĄny v ĆĄirokĂ© oblasti elektroniky a jsou zĂĄkladnĂ­mi stavebnĂ­mi bloky v analogovĂ©m zpracovĂĄnĂ­ signĂĄlu. V poslednĂ­ dekĂĄdě pro tento Ășčel bylo prezentovĂĄno velkĂ© mnoĆŸstvĂ­ stavebnĂ­ch funkčnĂ­ch blokĆŻ. V letech 2000 a 2006 na Ústavu telekomunikacĂ­, VUT v Brně byly definovĂĄny univerzĂĄlnĂ­ proudovĂœ konvejor (UCC) a univerzĂĄlnĂ­ napět'ovĂœ konvejor (UVC) a vyrobeny ve spoluprĂĄci s firmou AMI Semiconductor Czech, Ltd. OvĆĄem, stĂĄle existuje poĆŸadavek na vĂœvoj novĂœch aktivnĂ­ch prvkĆŻ, kterĂ© nabĂ­zejĂ­ novĂ© vĂœhody. HlavnĂ­ pƙínos prĂĄce proto spočívĂĄ v definici dalĆĄĂ­ch pĆŻvodnĂ­ch aktivnĂ­ch stavebnĂ­ch blokĆŻ jako jsou differential-input buffered and transconductance amplifier (DBTA), current follower transconductance amplifier (CFTA), z-copy current-controlled current inverting transconductance amplifier (ZC-CCCITA), generalized current follower differential input transconductance amplifier (GCFDITA), voltage gain-controlled modified current-feedback operational amplifier (VGC-MCFOA), a minus-type current-controlled third-generation voltage conveyor (CC-VCIII-). PomocĂ­ navrĆŸenĂœch aktivnĂ­ch stavebnĂ­ch blokĆŻ byly prezentovĂĄny pĆŻvodnĂ­ zapojenĂ­ fĂĄzovacĂ­ch člĂĄnkĆŻ prvnĂ­ho ƙádu, univerzĂĄlnĂ­ filtry druhĂ©ho ƙádu, ekvivalenty obvodu typu KHN, inverznĂ­ filtry, aktivnĂ­ simulĂĄtory uzemněnĂ©ho induktoru a kvadraturnĂ­ sinusoidnĂ­ oscilĂĄtory pracujĂ­cĂ­ v proudovĂ©m, napět'ovĂ©m a smĂ­ĆĄenĂ©m mĂłdu. ChovĂĄnĂ­ navrĆŸenĂœch obvodĆŻ byla ověƙena simulacĂ­ v prostƙedĂ­ SPICE a ve vybranĂœch pƙípadech experimentĂĄlnĂ­m měƙenĂ­m.Frequency filters and sinusoidal oscillators are linear electric circuits that are used in wide area of electronics and also are the basic building blocks in analogue signal processing. In the last decade, huge number of active building blocks (ABBs) were presented for this purpose. In 2000 and 2006, the universal current conveyor (UCC) and the universal voltage conveyor (UVC), respectively, were designed at the Department of Telecommunication, BUT, Brno, and produced in cooperation with AMI Semiconductor Czech, Ltd. There is still the need to develop new active elements that offer new advantages. The main contribution of this thesis is, therefore, the definition of other novel ABBs such as the differential-input buffered and transconductance amplifier (DBTA), the current follower transconductance amplifier (CFTA), the z-copy current-controlled current inverting transconductance amplifier (ZC-CCCITA), the generalized current follower differential input transconductance amplifier (GCFDITA), the voltage gain-controlled modified current-feedback operational amplifier (VGC-MCFOA), and the minus-type current-controlled third-generation voltage conveyor (CC-VCIII-). Using the proposed ABBs, novel structures of first-order all-pass filters, second-order universal filters, KHN-equivalent circuits, inverse filters, active grounded inductance simulators, and quadrature sinusoidal oscillators working in the current-, voltage-, or mixed-mode are presented. The behavior of the proposed circuits has been verified by SPICE simulations and in selected cases also by experimental measurements.

    Simple Floating Voltage-Controlled Memductor Emulator for Analog Applications

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    The topic of memristive circuits is a novel topic in circuit theory that has become of great importance due to its unique behavior which is useful in different applications. But since there is a lack of memristor samples, a memristor emulator is used instead of a solid state memristor. In this paper, a new simple floating voltage-controlled memductor emulator is introduced which is implemented using commercial off the shelf (COTS) realization. The mathematical modeling of the proposed circuit is derived to match the theoretical model. The proposed circuit is tested experimentally using different excitation signals such as sinusoidal, square, and triangular waves showing an excellent matching with previously reported simulations

    Applications of the optical fiber to the generation and to the measurement of low-phase-noise microwave signals

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    The optical fiber used as a microwave delay line exhibits high stability and low noise and makes accessible a long delay (>100 microseconds) in a wide bandwidth (about 40 GHz, limited by the optronic components). Hence, it finds applications as the frequency reference in microwave oscillators and as the reference discriminator for the measurement of phase noise. The fiber is suitable to measure the oscillator stability with a sensitivity of parts in 1E-12. Enhanced sensitivity is obtained with two independent delay lines, after correlating and averaging. Short-term stability of parts in 1E-12 is achieved inserting the delay line in an oscillator. The frequency can be set in steps multiple of the inverse delay, which is in the 10-100 kHz region. This article adds to the available references a considerable amount of engineering and practical knowledge, the understanding of 1/f noise, calibration, the analysis of the cross-spectrum technique to reduce the instrument background, the phase-noise model of the oscillator, and the experimental test of the oscillator model.Comment: 23 pages, 13 figures, 41 reference

    A miniature tunable quadrature shadow oscillator with orthogonal control

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    This article presents a new design of a quadrature shadow oscillator. The oscillator is realized using one input and two outputs of a second-order filter cell together with external amplifiers in a feedback configuration. The oscillation characteristics are controlled via the external gain without disturbing the internal filter cell, following the concept of the shadow oscillator. The proposed circuit configuration is simple with a small component-count. It consists of, two voltage-different transconductance amplifiers (VDTAs) along with a couple of passive elements. The frequency of oscillation (FO) and the condition of oscillation (CO) are controlled orthogonally via the dc bias current and external gain. Moreover, with the addition of the external gain, the frequency range of oscillation can be further extended. The proposed work is verified by computer simulation with the use of 180 nm complementary metal–oxide–semiconductor (CMOS) model parameters. The simulation gives satisfactory results of two sinusoidal output signals in quadrature with some small total harmonic distortions (THD). In addition, a circuit experiment is performed using the commercial operational transconductance amplifiers LM13700 as the active components. The circuit experiment also demonstrates satisfactory outcome which confirms the validity of the proposed circuit
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