Circuit Design and Implementation of Dynamic Bias-Current Control on Push-Pull amplifiers
|關鍵字:||推挽式放大器之動態偏流控制;Dynamic Bias-Current Control on Push-Pull amplifiers|
Amplifiers are divided into several classes, class-A, AB and B or G…etc . Some of them differ only in their bias-current theoretically. In other words, by adjusting the bias-current of an amplifier, we can get one different class out of another as long as the original amplifier is properly designed. Besides that, when they are working, chances are their bias-current varies a lot due to a wide temperature change in their elements and/or some disturbance from outside. Then, an amplifier certified as high performance Class-A could possibly degrade to high bias-current class-AB. Or, even worse, it can be destroyed if its bias-current exceeds too much the preset value, because of the extremely high temperature inside the chassis that encloses this amplifier. In this thesis I propose a set of effective circuits to control bias-current dynamically at the output stage of a push-pull amplifier. That is, in an attempt to stabilize the bias-current while allows it to vary with input signal dynamically in order to reduce power dissipation, I borrow the idea of negative feedback technique and find out a way to realize it. At the same time I also show the varieties of its application on push-pull amplifiers. Finally, I spent lots of time to experiment some of those applications in more practical way and check their performance. Of course, simulations using MATLAB and SPICE are also presented. I hope this thesis can offer some good experiences to people who are interested in amplifier design and of the most wishes, give me any advice you have in your mind.