China
Africa
Explore chapters and articles related to this topic
Signal Characteristics
Published in Kevin Robinson, Practical Audio Electronics, 2020
Crossover distortion can take many varying forms, depending on the mechanism generating it. The two extremes shown in Figure 5.6 illustrate either end of the spectrum, but various other kinds of steps and deformations are possible. This kind of signal modification is less commonly utilised in distortion effects (although by no means unheard of). On the other hand, it is a problem commonly encountered in amplification circuits which use some form of symmetrical circuit architecture to perform amplification of the positive and negative portions of a signal. If the circuit is not correctly designed and appropriately configured or calibrated, then crossover distortion can be introduced at the point where the signal amplification task is handed over from one side of the circuit to the other. This most often takes a form close to the first of the two variants shown.
Lighting and Communications: Devices and Systems
Published in Zabih Ghassemlooy, Luis Nero Alves, Stanislav Zvánovec, Mohammad-Ali Khalighi, Visible Light Communications, 2017
Luis Nero Alves, Luis Rodrigues, José Luis Cura
Figure 2.26 shows a voltage-mode analog LED driver [12,13]. A preamplification stage is used to accommodate input signal to LED voltage swing. Later, a push-pull configuration is used in the output stage working as a voltage buffer with high current capability. The output signal is fed into an LED using a bias tee. The circuit shown in Figure 2.26 may work in two possible biasing classes, B or AB (depicted in the figure). Class B is characterized by not having any biasing condition applied to transistors Q1 and Q2; the input signal has to drive the transistors on. As it can be seen, for lower Vin values the transistor’s current is zero, resulting in no output signal. The distortion generated by class B amplifiers is known as crossover distortion, as it occurs when the input signal crosses the zero reference value. This is of limited usage as an LED driving configuration: the voltage span of the LED is usually less than the required voltage to turn on these transistors.
Output Stage Distortions
Published in Douglas Self, Audio Power Amplifier Design, 2013
This makes sense. We know that crossover distortion increases with heavier loading, i.e., with greater currents flowing in the output devices, but under the same voltage conditions. It is therefore not surprising that reducing the device currents by using multiple devices has the same effect as reducing loading. If there are two output devices in parallel, each sees half the current variations, and crossover non-linearity is reduced. The voltage conditions are the same in each half and so are unchanged. This offers us the interesting possibility that crossover distortion — which has hitherto appeared inescapable — can be reduced to an arbitrary level simply by paralleling enough output transistors. To the best of my knowledge, this is a new insight.
Fast-scale non-linear distortion analysis of peak-current-controlled buck–boost inverters
Published in International Journal of Electronics, 2018
Hao Zhang, Shuai Dong, Chuanzhi Yi, Weimin Guan
The waveforms of inductor current and output voltage under various value of reference voltage is shown in Figure 14. As can be seen from Figure 14(a), when the peak value of the reference voltage is set as , the circuit system can work in stable operation. It is observed that the zero-crossing distortion happens, which is marked by the red square in Figure 14(a,b), respectively. That is, the inductor current has a crossover distortion around the zero-crossing points at the beginning of each half one line period. Instead, when the peak value of the reference voltage increases to , the fast-scale period-doubling bifurcation occurs in the inductor current and the output voltage also suffers severe fluctuation during the same time, as shown in Figure 14(b). Furthermore, notice that the critical phase angle is shifted to the right side, which validate the analysis of Section 4. More specifically, from the closed-up view of Figure 14(b), i.e. Figure 14(c), it can be seen that the critical angle are about and , which is generally coincide with the theoretical analysis. Therefore, these experimental results are in accordance with those of the previously mentioned theoretical and numerical ones.
Design and Study of Novel Tunable ELF-PEMF System for Therapeutic Applications
Published in IETE Journal of Research, 2022
Himani Kohli, Sangeeta Srivastava, Manan Oza, Satish Chouhan, Shivani Verma, Anju Bansal, Bhuvnesh Kumar, Sanjeev Kumar Sharma
We therefore designed a power modulator that would boost the current to 2 A. We opted for TDA 2050 which is a high-fidelity power amplifier monolithic-integrated circuit [13] and produces very low harmonic and crossover distortion over the low-frequency range. The modulator circuit as shown in Figure 3 was designed to operate at variable supply from +15 to +30 V and tested for frequency ranging from 5 to 100 Hz. The impedance of the coil system is frequency dependent. Therefore, the supply voltage was varied to maintain the constant magnetic field strength at different frequencies.