x切换电路是视频软开关(慢转换、特技波控、色键等)的核心电路。现在六晶体管带恒流源双差分电路,由于其简单、灵活、控制时输出直流电平不变、可以直流遥控、便于集成化等特点已成为应用最广泛的x切换电路。由于理论分析结论是在晶体管参数完全对称的前提下作出的,而实际上“对称”是相对的,“不对称”是绝对的,从而出现了用分立元件时如何选配晶体管,对集成器件应如何合理提出参数对称性要求,以及如何通过电路中配置适当调节元件来补偿晶体管参数的不对称,以降低电路对晶体管苛求等问题,本文对因参数不对称而出现的种种问题作了分析,并得出相应结论。在分析的基础上提出了电路的直接、间接调试法,可将晶体管的各参数一一转化为等效的电位器调节作用,用示波器显示调节波形,使调节达最佳,试验结果与理论分析一致,并表明此法合理、准确、迅速。最后讨论了控制的线性化问题,使导演效果更趋理想。 x switching circuit is the video soft-switching (slow conversion, special wave control, color keys, etc.) of the core circuit. Now six transistors with a constant current source dual differential circuit, because of its simple, flexible, DC output control unchanged, DC remote control can be easily integrated features such as has become the most widely used x switching circuit. As the conclusion of the theoretical analysis is made under the premise of complete symmetry of the transistor parameters, in fact, “symmetry” is relative and “asymmetry” is absolute. Therefore, how to select a transistor when using discrete components, How to reasonably propose the parameter symmetry requirements and how to compensate the asymmetry of the transistor parameters by adjusting the appropriate components in the circuit so as to reduce the circuit demanding on the transistors and so on are discussed in this paper. Draw the corresponding conclusion. On the basis of the analysis, a direct and indirect method of the circuit is proposed. The parameters of the transistor can be converted into the equivalent potentiometer adjustment function. The oscilloscope can be used to display the adjustment waveform so as to achieve the best adjustment. The test results and the theory Analysis of the same, and that this method is reasonable, accurate and rapid. Finally, we discuss the linearization of control and make the effect of director more ideal.