A multi-band fast-locking delay-locked loop with jitter-bounded feature

In this paper, a fast-locking delay-locked loop (DLL) with jitter-bounded feature is presented. In the proposed fast-locking mechanism, a frequency estimator and a programmable voltage circuit are developed to rapidly switch the control node of voltage-controlled delay line to a voltage level near the final required value. After that, the DLL output will be quickly locked by the following charge pumping on the loop filter. In the jitter-bounded approach, two phase-frequency detectors and a tunable delay are employed to hold the output clock jitter between two reference inputs after the DLL is locked. Furthermore, to enhance the flexibility of the presented DLL, a frequency multiplier with fewer active devices is also developed to provide high-frequency clock output for wideband applications. The presented DLL is implemented in a 0.18-μm 1P6M CMOS technology. The active area without contact pads is 0.34 × 0.41 mm(2). A minimum lock time of six clock cycles is measured from no reference input to locked state. The output frequency ranges of the DLL and the frequency multiplier can be measured from 200 to 400 MHz and from 1 to 2 GHz, respectively. The power dissipation of the presented DLL is 31.5 mW at a 1.8 V supply voltage.     

一种脉宽调制的高稳定连续可调直流电压源

介绍了一种以深埋齐纳电压基准元件LTZ1000A主电路为基础,结合脉宽调制技术实现的在0～10 V范围内连续可调的高稳定直流电压源。选用精密电阻并采用适当的保温与隔离措施,实现了电压基准主电路输出高稳定7 V电压,其短期稳定性达到1.7×10^-8。利用具有相同温度系数和阻值的精密电阻组成比例升压电阻网络,使输出10 V电压的短期稳定性为2.4×10^-8。同时利用脉宽调制并经DC-DC转换电路及滤波电路得到0～10 V的电压输出,短期稳定性可在10^-7量级左右。     

Evaluation of the design requirements for the electrical part oftransmission-type optical smoke detector to improve its thresholdstability to slowly varying influences

The output signal sensitivity to optical component contamination and other slowly varying parasitic influences in the transmission-type smoke detector is analyzed. The analysis carried out the new topology characterized by the selective feedback loop incorporating the optical part of the detector. Depending on the loop gain frequency shaping in the electrical part of the loop, dual-stability enhancement of the input threshold level can be achieved. The stable dc output signal can be preserved by the high dc loop gain value, as an option to the standard serial filter dc rejection. The detector passband gain stability is achieved by the high loop gain selectivity, eliminating feedback at very low or passband frequencies. The proposed topology can be easily adopted to both digital and low-cost analog detector designs. The special case of the threshold sensitivity neutralization through the cancellation of the output dc signal sensitivity and passband gain sensitivity is considered, too, as an option suitable for low-cost detectors. In addition to the described linear settlement, two nonlinear solutions are presented, the first of them based on the foregoing linear circuit analysis. Despite its nonlinear nature, this alternative solution is not troublesome for analog implementation, since the nonlinear function required is realized by the standard variable gain amplifier. Another nonlinear method requires logarithmic function implementation, so that its suitability depends on the particular design requirements     

Recent Advances in High-Frequency Performance of Feedback Amplifier-Transformer Combinations

The high-frequency limitations inherent in systems dependent upon performance of amplifier-transformer combinations have often restricted ac calibration in the high audio range. Three recent advances in design of feedback amplifiers incorporating transformers make possible significant improvements in bandwidth, linearity, and computing accuracy in this range. The first method compensates for the leakage reactance-output capacitance resonance that frequently constitutes the basic bandwidth limitation in feedback amplifier systems which incorporate output transformers. The second approach introduces resonant stabilization, allowing more loop gain for distortion reduction at specific harmonics. The third technique employs two or more computing amplifier-ratio transformer combinations effectively in parallel. This configuration can yield worst-case computing errors inversely proportional roughly to loop gain raised to a power equal to the number of parallel combinations. Applications of the three techniques in a practical, all-solid-state 20 kHz ac calibration source are described. The output amplifier-transformer combination supplies an external load with 20 VA to 20 kHz and 1 kV, with distortion of 0.03 to 0.05 percent at the high-frequency end. At the same time, parallel sets of computing amplifier-ratio transformer combinations within the source furnish ratio transformer scaling accuracy in division. This, in turn, permits overall linearity which is typically ±0.01 percent to 5 kHz, ±0.02 percent to 20 kHz, over a ten-to-one output amplitude range, expressed in percent of local (rather than full-scale) output voltage.     

A magnetic feedback modulator for improved FM carrier recording

Magnetic multivibrators are often used as voltage-controlled oscillators in FM carrier recording systems. These oscillators generally consist of two switching transistors connected to a center tapped coil on a square loop magnetic core. The transistors operate alternately in saturation, driving the core between its positive and negative saturation limits. Frequency then depends upon saturation flux and applied voltage. In the Magnetic Feedback Modulator, stability and linearity improvement of an order of magnitude is possible with a new method of applying negative feedback to a square-loop core magnetic multivibrator. In addition, circuit complexity is reduced considerably over previous methods using conventional frequency detectors to derive feedback voltage. Based on Faraday's Law, a voltage which is a function of frequency and flux change is derived from the magnetic circuit. This voltage is then used as negative feedback to the dc differential amplifier to drive the magnetic multivibrator. Since the magnetic circuit is included in the negative feedback loop, frequency errors occurring in the modulator cause corresponding changes in the magnetic feedback voltage. The errors are then reduced in magnitude by the negative feedback.     

On the dynamic properties of cascaded self-saturating magnetic amplifiers

The influence of some parameters of the 2-stage self-saturating magnetic amplifier on its steady-state and transient properties is described. It is shown that applying anR,Cfilter between both stages ensures proper operation of the amplifier. On the basis of the difference equations describing the single stage self-saturating magnetic amplifier, the discrete transmittance of the circuit can be derived. It is pointed out that the back reaction of the second stage on the first appears in cascade. The time constants of the cascade are not equal to the time constants of stages working separately. The influence of the electric and magnetic feedback loop over both stages on the stability of the circuit is considered. There are given conditions under which, when the transient state is caused by a jump change of control voltage, the cascade output voltage appears as an exponential function with two time constants, damped oscillations, or self-sustained oscillations. Characteristic parameters of the cascaded magnetic amplifier are determined. Theoretical results were compared with laboratory investigations.     

Detections of secondary current and torque of induction motors using amorphous microcore field sensors

New secondary-current sensors for squirrel-cage induction motors are presented using a multivibrator with two group amorphous microcores. The 8-pair micro cores are set near the both endrings of a rotor for cancellation of the influence of unstable rotor motion on sensing of the secondary current. Electromagnetic torque was detected as an output voltage of a multiplier for the secondary current and the main flux. The main flux was detected using a multivibrator-type flux sensor utilizing two stator teeth as two cores. A possible new control system for variable speed induction motors with a torque feedback loop is discussed, which stably works independently of variations of motor parameters.     

An automatic pressure controller for vacuum systems

This paper describes the development of a closed loop servo-system designed to control gas throughput so as to maintain a constant pressure in a dynamic vacuum system. It is designed to work with pressure gauges having an electrical output signal and gas inlet needle valves adaptable for drive by a small servo motor. Traditional principles of operation are adopted, the gauge output signal after amplification being compared with a reference voltage. The difference between the two, controls the drive to the motor. The motor drive is in such a direction as to tend to maintain the pressure gauge output voltage equal to the reference. It is important that the system provides a rapid and stable closed loop response for widely varying types of operation with gauges having a fast response (e.g. ionization types) or slow response (e.g. Pirani type) and also with both long and short vacuum time constants.     

Ultra low-noise current sources

The solid state DC current sources available on the market are not suitable for applications in low noise measurement systems because of the high level of low-frequency noise introduced in the measurement chain. The most important cause of low-frequency noise in such instruments is the solid state device used as a voltage reference (usually a Zener diode). This problem has been solved, in the instrument described in this paper, by using a new circuit topology in which the solid-state voltage reference has been substituted by a low-noise battery. The instrument, capable of supplying a current as high as 100 mA, is characterized by a low-frequency noise level some orders of magnitude lower than that of similar commercial instrumentation     

Analog-Multiplier Circuit Linearizes Transducer Output

A circuit employing one operational amplifier and one analog multiplier is used to produce a voltage output proportional to the quantity t when the input voltage is related to t (e.g., temperature) by at + bt2, where a and b are constants. The determination of the resistor values, the useful operating voltage range, the accuracy of the linearizing process and the effects of changes in the ambient temperature are discussed. Extension of the circuit to higher order polynomial functions is also considered.     

Phase shifter: a nonlinear circuit for direct measurement of phasemargin in feedback control systems

A novel nonlinear circuit called a “Phase Shifter” is introduced which accurately measures the phase margin of a linear system operating in a feedback control loop. The measurement is made by inserting the phase shifter in the control loop, causing it to undergo self-sustained oscillations (limit cycle) of relatively low amplitude. It is shown that sustained oscillations occur at the gain crossover frequency, and the phase margin is equal to the phase lag of the inserted circuit. A complete analysis of the amplitude and frequency of oscillation, which employs the classical sinusoidal-input describing function, is also given and the stability of the limit cycle and its neighborhood, using the theory of integral manifolds, is included     

Voltage-controlled narrowband and wide, variable-range four-segment quartz crystal oscillator

In this work, our goal is to develop a voltage-controlled variable-frequency quartz crystal oscillator with narrowband response, wide, variable frequency range and the capacity to oscillate across the series resonance frequency using a four-segment configuration of a quartz crystal oscillator. In conventional quartz oscillators, the quartz resonator is inserted in the feedback loop between the input and the output of the active circuit, providing sufficient gain and the phase relation. In the oscillator developed here, the quartz crystal resonator is inserted between the loop circuit and the ground potential. The performance of the voltage-controlled variable-frequency oscillator is demonstrated across the series resonance frequency.     

A bootstrap voltage reference based upon an N-type negativeresistance device

A circuit that develops a reference voltage based upon the stability of the current of an N-type negative-resistance device (NNRD) in the neighborhood of the current peak is described. The NNRD is self-driven in a bootstrap configuration utilizing a single operational amplifier, with the bias circuit acting as a stiff voltage source having a negative Thevenin equivalent DC resistance. The analysis is specialized to the case of a particular NNRD, a p-n junction tunnel diode (TD), and a series of matching networks coupling the TD to the remainder of the bootstrap circuit are analyzed to demonstrate that a properly matched TD, biased by this bootstrap circuit, can be made stable against oscillation. The regulation of bias fluctuations, noise performance, temperature stability, and immunity to neutron damage are reviewed. Comparison is made to avalanche-diode-based bootstrap references. NNRD-based voltage references may have an impact in circuits and material systems where fabrication of high-quality Zener devices is not possible     

A three-phase magnetic amplifier: I--An analysis

An analysis is presented of a 3-phase magnetic amplifier with bridge-connected output circuit and any number of series-connected and parallel-connected control windings. Approximate output difference equations are derived for two modes of operation representing one-half to minimum output and one-half to full output. These output difference equations express the dynamic relationship of the sixth-cycle average input and outputvoltages in terms of a core function and the control circuit resistances. The importance of a feedback factor associated with the fraction of the voltage from a gating core which appears across the cores in a position to be reset is demonstrated. Approximate gain and time constant expressions appropriate for a simplified dynamic representation are derived from the difference equations and a more complicated block diagram representation.     

An AC-DC Ratiometer and Its Use in a CRL Meter

An impedance meter is described which measures dc resistance and ac capacitance and inductance. It uses an ac-dc ratiometer capable of high accuracy and good noise immunity. The ratiometer is a combination of a dual-slope integrator and an integrating phase-sensitive detector. The ratio, which is displayed on a counter, is the number of denominator signal samples required to offset a prescribed number of numerator samples. The remainder output, if important, can be evaluated by a sinple dual-slope integrator to provide the readout digits of lesser significance. The same circuit is used for both ac and dc ratios and could be used to detennine the ratio of the average value of an ac voltage to a dc voltge.     

A Very Low Offset Preamplifier for Voltage Measurements in the $muhbox{V}$ Range

A new topology for the implementation of a very low offset voltage preamplifier is presented. The new topology employs a time-varying resistance as a probe for detecting the sign and magnitude of the equivalent input offset of an operational amplifier in a series-shunt feedback configuration and allows for continuously correcting the offset voltage by means of a proper control feedback. The most remarkable feature of the approach we propose is the fact that the offset correction can continuously be performed with the signal voltage source connected to the circuit, as its presence and magnitude do not affect the offset detection circuit. At the same time, the offset cancellation circuit has minimum effect on the output voltage of the preamplifier in the bandwidth of the signal. An actual low-offset preamplifier based on the new approach we propose has been built and tested. While employing a metal–oxide–semiconductor field-effect transistor (MOSFET) input operational amplifier with a typical input offset of 100 $muhbox{V}$ (600- $muhbox{V}$ maximum), a voltage preamplifier with a gain of 201 and an equivalent input offset voltage below 100 nV is consistently obtained, which is independent, by design, of the temperature. While characterized by these excellent performances, the system employs quite standard low-cost components and does not require any calibration procedure.      

Measurement of Operational Amplifier Characteristics in the Frequency Domain

A test circuit for the automatic measurement of integrated-circuit operational amplifiers in the frequency domain has been developed. The main advantage of this test circuit over those previously reported in the literature is that it uses buffers in the feedback loop to reduce the influence of the output impedance of the operational amplifier. A fit program has been developed to extract the relevant parameters such as the transfer characteristics, the common mode rejection ratio, and the power supply rejection ratio. Examples of measurements are added for several operational amplifiers.     

一种线性保护输入的恒压LED驱动电源设计

采用对母线电压进行反馈调节的恒压控制方式,设计研究了一种新型高压(260AC)线性保护输入LED驱动电路.利用LD7591GS芯片控制的脉冲宽度调制(PWM)电路和外围光耦电压反馈电路以及LNK564芯片控制的线性隔离变换电路,通过对驱动电路拓扑结构进行研究设计,并对变压器参数进行优化,实现了电压反馈的线性保护输入LED驱动电源设计.实验结果表明,采用外围电压反馈方式电路和线性隔离保护电路调整的LED驱动电源电路具有较好的安全稳定特性和低纹波PWM输出波形,并具有高转化效率,良好的抗电磁干扰性能和稳定的恒压功能.     

Modeling and analysis of dual-output piezoelectric transformer operating at the thickness-shear vibration mode.

In our previous study, the multioutput piezoelectric transformer operating at the thickness-shear vibration mode was proposed and experimentally investigated. By designing a new construction of support and lead wire connection, a power density of 52.7 W/cm3 and a total output power of 169.8 W were achieved at a temperature rise less than 20 degrees C. In this work, a theoretical model was developed for the dual-output piezoelectric transformer operating at the thickness-shear vibration mode. The equivalent circuit parameters of the piezoelectric transformer were derived. Based on this, the impedance characteristics, equivalent inductance, capacitance ratio, voltage gain, and efficiency of the piezoelectric transformer were calculated. The theoretical results were verified by experimental data. Furthermore, the effect of the transformer size on the voltage gain, efficiency, output power and power density, and the effect of the load of one output on the voltage gain of another output were analyzed. Some useful guidelines were achieved by these analyses.     

基于状态空间的PWM逆变器数字PI双环控制技术研究

主要研究了数字控制的实际应用情况以及脉宽调制(PWM)正弦波逆变器的特点,包括电流内环电压外环的双闭环控制。在建立逆变器控制系统状态空间模型的基础上,详细分析了外环为输出电压,内环为电感电流加负载电流前馈控制对应的控制策略的稳定性和动态响应。先对控制系统直接离散化,再利用极点配置的方法进行系统参数设计。从响应速度、外特性、稳定性方面进行了具体分析,结果说明在离散域里双环控制逆变器具有较好的动态响应速度和输出外特性。最后通过实验验证和仿真波形分析,证明这种双环控制技术能满足各项性能指标要求。