放大电路频率特性的逆向启发式教学研究

摘要

“放大器的频率特性”是《模拟电子技术基础》课程中的教学难点，在学时分配有限的情况下该内容的教学方法是否得当将直接影响学生对于放大器特性的完整理解。遵照国内外主流教材，仍然以基本的单管共射放大电路为例，首先引出电路完整的电压放大倍数表达式，在启发学生思考中将频率特性的分析转变为对上、下限频率的简单求解；然后根据电容容抗的表达式对放大电路中的耦合电容与结电容进行分频段研究；分析RC低通、高通电路的频率特性及分别对应的上、下限频率，并很自然地引出晶体管的高频小信号Π形等效电路；最后根据学生的专业与学时有区别地化简等效电路，验证放大器的频率特性，得到放大电路的完整波特图。%Amplifier frequency response is one of the teaching difficult points in the course of“Analog Electronic Technology Foundation”. The teaching ways and means for this section will have direct impact on students comprehension towards amplifiers amplifying characteristic. Based on the mainstream teaching materials both at home and abroad,and taking the single transistor common emitter amplifier circuit as teaching example,an expression of the voltage amplifying factor is firstly introduced,and students are inspired to think about the simple solutions of upper and lower frequencies rather than frequency response. Then spectrum research method is used to study the coupling capacitance and the junction capacitance according to the expression of capacitive reactance. Thirdly,the frequency characteristics of RC low-pass circuit and the high-pass circuit are simply analyzed, thus the high frequency small signal Π equivalent circuit is naturally appeared. The simplied equivalent circuit is deduced dis-criminatively according to the student′s major and school. The amplifier frequency response is verified and the complete Potter figure is obtained finally.