有源环路低通中运放带宽对相噪的影响

Effect of operational amplifier on phase noise in active low-pass loop

锁相环是无线电系统的重要组成部分.在使用宽带压控振荡器的宽输出锁相环中,为了满足压控振荡器的调谐电压范围,使用运算放大器构建的有源环路低通是锁相环必不可少的组成部分.本研究从运算放大器单位增益带宽的角度,运用仿真手段,详细阐述该运放指标对锁相环相位噪声的影响,并选用两款不同的运放进行对比测试,进而得出设计过程中的选型指南.

PLL is an important part of wireless system.In the wide-output PLL using wideband VCO,the active low-pass loop filter constructed by operational amplifier is an essential part in order to meet the tunable voltage range.In this paper,the influence of the operational amplifier unit gain bandwidth on the PLL phase noise is described in detail by means of simulation.At last,two different operational amplifiers are selected for comparative testing and then the selection guide is obtained.