Synthesis of oscillator circuits employing only one unity-gain amplifier

A simple method to synthesise oscillator circuits employing only one unity-gain amplifier is presented. It is shown that any oscillator formed by one inverting infinite-gain ideal amplifier looped back by a perfect band-reject filter will automatically give rise, through a simple transformation, to an oscillator circuit employing only one unity-gain amplifier. It is further shown that the passive network must be at least a third-order band-reject filter.     

RC-active filters using unity-gain amplifiers

A new active-filter configuration consisting of RC elements and a single unity-gain amplifier is suggested. The method may realise many useful 2nd-order transfer functions with a small number of RC elements.     

Switched-capacitor filters using unity-gain amplifiers

Switched-capacitor networks realizing second-order filter characteristics are presented. Realization is achieved with unity-gain amplifiers as buffers. The circuits have small sensitivities, good dynamic range and a reasonable spread of capacitor values. The filters can be used for high-Q realization and a relatively high frequency range.     

Design techniques for high-frequency CMOS switched-capacitorfilters using non-op-amp-based unity-gain amplifiers

A fully differential non-op-amp-based unity-gain amplifier (UGA) is proposed, whose 3-dB frequency can be as high as 250 MHz in 3.5-μm p-well CMOS technology. The purpose is to develop a new design concept for high-frequency switched-capacitor (SC) filters which uses balanced non-op-amp type UGAs with tunable gain to replace conventional op-amp-based unity-gain buffers (UGBs). The proposed UGA has a normal gain of unit, but it has a greater bandwidth, better setting behavior, smaller chip area, and less transistors than op-amp-based UGB. The new UGA also has a fully differential balanced configuration. The balanced configuration and proper predistortion by CAD tools can reduce the error due to linear parasitic capacitances. Experimental results prove the capability of the proposed structures in the realization of high-frequency SC filters over the megahertz range     

New current-conveyor-based single-resistance-controlled/voltage-controlled oscillator employing grounded capacitors

A new current conveyor (CC) based minimum-component oscillator structure has been proposed which provides the following advantageous features over the previously known minimum-component designs: (i) noninteracting control of frequency of oscillation through a single grounded resistor, (ii) easy convertibility into a voltage-controlled oscillator (iii) use of two grounded capacitors as preferred for IC implementation, (iv) availability of a buffered output, and (v) very good frequency stability.<>     

Novel sinusoidal oscillator employing grounded capacitors

An earlier single-resistance-controlled oscillator (s.r.c.o.) with grounded capacitors employs three operational amplifiers (o.a.); the new s.r.c.o. proposed here employs only two o.a.s and a reduced number of resistors. The proposed s.r.c.o. may be adopted for voltage-controlled-oscillator realisation. In addition, the new circuit may also be employed for the generation of very-low-frequency oscillations. The circuit appears to be suitable for integrated-circuit implementation.     

Current mode biquadratic filter realizations employing operational amplifiers

New circuit configurations for realizing current mode biquadratic filter sections using operational amplifiers are presented. Each circuit uses a single operational amplifier and seven passive elements at most. The merits and demerits of the proposed realizations are discussed.     

Current-mode KHN filter employing current differencing transconductance amplifiers

This study proposes a current mode (CM) Kerwin–Huelsman–Newcomb (KHN) filter employing only two current differencing transconductance amplifiers (CDTA) and two grounded capacitors. It is concluded that the circuit described here offers a simpler and more economical alternative to other CM KHN filters reported previously in literature.     

Short-pulse generation in interferometers employing semiconductor optical amplifiers

Short light pulses can be generated by interferometer systems commonly used as all optical switches in telecommunication applications. The method of pulse generation does not involve lasing and transforms an optical square-wave input with slow rise times into a short-pulse train. A mathematical model for the system is developed. Conditions for correct operation of the system are derived from the model. Simulations illustrate the system operation. Furthermore, initial experiments are performed using a combination of fiber and free space optics. The experiments demonstrate the controllable pulse width and obtain pulsewidths of down to approximately 1 ps.     

Linear resistance-to-frequency conversion employing integrated circuit operational amplifiers

A simple approach is presented for synthesizing linear R/f converters which may be useful in measurement systems employing restive transducers. Four R/f converters are derived each of which employs only three integrated circuit operational amplifiers along with a few RC components. Experimental results are found to be in agreement with the theoretical values.     

A multisensor employing an ultrasonic Lamb-wave oscillator

Initial experimental, analytical, and numerical evaluations of a microsensor that uses ultrasonic Lamb waves propagating in a thin plate supported by a silicon die are presented. Changes of oscillator frequency indicate magnitudes of the variables sensed. Because it is sensitive to many measurands, the device could operate as a microphone, biosensor, chemical vapor or gas detector, scale, pressure sensor, densitometer, radiometer, or thermometer. Because it is based on the use of Lamb waves, the sensor has selective response and sensitive operation in the low-megahertz frequency range in vacuum, in a gas, or while immersed in a liquid     

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.     

New universal biquad filters using only two unity-gain cells

New current-mode and voltage-mode universal biquad filters are presented using only two unity-gain cells (one current follower and one voltage follower) in each configuration. The proposed filters employ one less follower than in the literature to date. The filters can realize highpass, bandpass, lowpass, notch and allpass responses without any changes in the circuit topology. The circuits enjoy the following advantages: minimum number of active elements, no component-matching condition and low active and passive sensitivities.     

Coherent operation of monolithically integrated master oscillator amplifiers

Monolithically integrated master oscillator power amplifiers have been fabricated. The oscillator is a second order distributed Bragg reflector (DBR) laser. The epitaxial layer structure consists of a double quantum well active region bonded by Al/sub 0.3/Ga/sub 0.7/As confining layers and Al/sub 0.4/Ga/sub 0.6/As cladding layers. The resultant output is a single longitudinal mode in a nearly diffraction limited output to a power level of 485 mW.<>     

采用迟滞比较器的自激振荡功率放大器行为特性分析

采用迟滞比较器的自激振荡功率放大器,在音频功放、DSL线路驱动器及数据转换器等方面得到了较好的应用。但由于其强非线性的特性,分析其行为特性较为困难。本文从时域出发分析了1阶和2阶系统的振荡频率,以线性化的比较器增益为基础分析了系统增益,给出了3次谐波失真的经验公式,不仅简洁、直观,而且具有较高的精度。这些结果经Matlab仿真验证,可以给电路设计者较好的指导作用。     

Gain-shifted thulium-doped fibre amplifiers employing novel highconcentration doping technique

A novel high thulium concentration doping technique is proposed for shifting the gain band in thulium-doped fibre amplifiers (TDFAs). The gain peak shifts from 1473 to 1505 nm when the Tm³⁺ concentration is increased from 2000 to 8000 ppm. The authors have achieved gains of >18 dB and a noise figure (NF) of <7 dB from 1480 to 1510 nm (30 nm bandwidth) for a total pump power of 500 mW     

Fibre-optic filters employing optical amplifiers to provide design flexibility

It is shown that optical amplifiers (OAs) can provide extra flexibility for unique fibre-optic designs, not available in passive configurations. Results are presented for both amplified and unamplified fibre-optic recirculating delay lines (AFORDL and UFORDL) indicating that the AFORDL is capable of realising filters not possible with the UFORDL.<>     

Novel allpass filter configuration employing single OTRA

A new circuit configuration uses a single operational transresistance amplifier (OTRA) and four passive elements to realize both first- and second-order allpass filters. Owing to internal grounding of the OTRA input terminals, effects of input parasitics are significantly reduced. Applications of the circuit include the realization of the phase equalizer, the quadrature oscillator, and the high-Q bandpass filter for analog signal processing. The performance of the allpass filter is illustrated by circuit-level simulation of a quadrature oscillator with CMOS realization of the OTRA.     

Distortion of FM modulation in injection phase-locked oscillator amplifiers

A generalized Adler's equation for the injection-locking phenomenon is presented. The method for its approximate solution is then discussed. The modulation frequency dependence of the total nonlinear and delay distortion of the FM modulation in an injection phase-locked oscillator-amplifier is presented graphically, with either peak frequency deviation or gain as a parameter.     

980-nm master oscillator power amplifiers with nonabsorbing mirrors

High-power master oscillator power amplifiers with nonabsorbing mirrors have been fabricated. These devices exhibit 1.0 and 1.5 W of single-frequency diffraction-limited continuous-wave optical powers at relatively low-amplifier currents of 1.75 and 2.6 A, respectively. These devices operate with a single longitudinal mode with a 40-dB sidemode suppression ratio over the entire amplifier current range without any longitudinal mode hops as a result of the very low optical feedback from the PA facet. Coupling of over 500 mW into a single-mode fiber is also achieved