基于电阻元件定性效用分析的电路可稳定振荡性判定方法

Determination method for potency of stable-oscillation based on qualitative effect analysis of resistor

相量形式的电路起振条件中,在谐振频率ω1处环路增益的幅角对频率的偏导■符号是电路的一个关键特征.对于内含RLC串联结构或RLC并联结构作为谐振选频环节的电路,一般性地推导出了谐振选频环节中电阻元件的参量(电阻值或电导值)变化或频率变化所引起的环路增益模变化和幅角变化之间的关系.据此得到了判断这一偏导符号的严谨而方便的定性方法,此方法简单到只需分析谐振选频环节中电阻元件的参量(电阻值或电导值)变化对于环路增益的定性影响效用即可.论证了电路中同一位置处选取RLC串联结构或RLC并联结构作为谐振选频环节时,两种情况下得到的这一偏导符号相反.这一偏导的符号对于定性判断采用常规放大器件的电路是否具备依赖于内稳幅的可稳定振荡性起着重要作用.当这一偏导的符号不满足可稳定振荡的要求,则只需要将谐振选频环节的内部连接方式(串联或并联)变更一下就能解决问题.这种定性分析也为新型LC振荡器的设计提供了可能性.

The en-oscillation conditions in the form of phasor method show that the sign of partial derivative ■ is an important feature of the circuit.For the circuit with series RLC structure or parallel RLC structure as the resonant unit,the relationships between the amplitude variation and the argument variation of the loop gain caused by the resistor-parameter(resistance value or conductance value)change or frequency change in the resonant unit are deduced.Therefore,a rigorous and handy method to determinate this partial derivative sign is obtained,which is effectuated by simply analyzing the qualitative effect of the resistor-parameter(resistance value or conductance value)change in the resonant unit on the loop gain.It is proved that when series RLC structure or parallel RLC structure serves as the resonant unit in the circuit,this partial derivative sign is opposite in the two cases.This partial derivative symbol plays an important role in determining whether the circuit with conventional amplifier has the potency of stable-oscillation dependent on internal amplitude stability.It is found that even if the sign of this partial derivative does not meet the requirement of stable-oscillation,just change the internal connection pattern(series or parallel)of the resonant unit.This qualitative analysis also inaugurates rich possibilities for the design of new LC oscillators.