| Power ampliifer is widely used in all kinds of communication systems, and thestudy of power ampliifer of this paper is mainly used in the electromagnetic wavelogging while drilling equipment. Power amplifier is one of important components ofthe transmitter of electromagnetic wave logging while drilling equipment, it issignificant to research and develop a kind of high eiffciency power amplifier to improveelectromagnetic wave logging while drilling equipment performance for the complexenvironment in the downhole. The traditional power amplifier, such as class A，class B,and class C power amplifier, atfer decades of development, has become maturetechnology, but eiffciency improvement of these power amplifiers is to reduce thetransistor tunr-on angle or to increase the input power, which has restricted these poweramplifiers to get higher eiffciency.Compared with the traditional linear power amplifier, the switch mode poweramplifier, such as class D，class E and class DE power ampliifer, has higher eiffciency.The switch mode power ampliifer overcomes shortcomings of the traditional linearpower ampliifer, the transisor works as a switch, at any time, voltage or current in thetransistor is very small, and even tends to zero, thus to reduce the transistor power lossand improve eiffciency of the power amplifier.The main work of this paper is the study of high eiffciency class DE poweramplifier. Class DE power amplifier integrated advantages of class D and class E poweramplifier, inherited the high efficiency characteristic of switch mode power amplifier,avoided shortcomings of class D and class E power amplifier, voltage and current in thetransistor would not appear at the same time, there are also no higher requirements tothe transistor for working current and voltage.Firstly in the paper, power amplifier devices, performance parameters, power ampliifer common types were introduced, and then a detailed analysis of class DEpower amplifier including circuit characteristics, circuit performance and element valuewere given. Nonlinear shunt capacitance of class DE power amplifier was discussed,finally proved correctness of theoretical analysis by using SPICE simulation program.Study of class DE power ampliifer can be summarized as follows:(1)Analysed class DE power amplifier detailedly, provided basic circuit diagramand equivalent circuit diagram of class DE power amplifier. Class DE power amplifiercircuit characteristics were analysed, values and waveforms of currents and voltages inthe circuit, and formulas of each element in the circuit were provided.(2)Discussed the effect of nonlinear shunt capacitance on class DE poweramplifier. Provided the expression of shunt capacitance which combined by an externallinear capacitance and MOSFET parasitic capacitance for any grading coeiffcient at the25%duty ratio through theoretical analysis. In the analysis, an equivalent linear shuntcapacitance of nonlinear MOSFET parasitic capacitance was defined, which improvedthe design precision of class DE power ampliifer and kept the high efifciencycharacteirstic of class DE power amplifier.(3)Designed class DE power amplifier by using SPICE simulation program,compared simulation results with class D and class E power ampliifer and veriifedadvantanges of class DE power amplifier. Class DE power amplifier with nonlinearcapacitance was simulated and correctness of the analysis was verified, which improvedwork efifciency of class DE power amplifier.With the development of wireless communication technology, the requirement forthe performance of power amplifier is increasing. Due to the advantage of higheiffciency formed by its own structure, class DE power amplifier has higher researchvalue and wider research space. |
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