一种用于自稳零放大器的伪随机信号发生器

A pseudo-random signal generator for auto-zero amplifier

提出了一种用于自稳零运算放大器的伪随机信号发生器电路.该电路结合了线性反馈移位寄存器和多级计数器,实现了输出信号的频率在一定范围内随机变化的功能.利用7级线性反馈移位寄存器生成的7位伪随机码对多级计数器进行置位,计数器以置位后的状态开始计数.当计数器计满时,输出信号跳变一次.同时,线性反馈移位寄存器生成新的伪随机码对计数器电路进行重新置位,计数器再重新计数.最终产生频率在一定范围内随机变化的输出信号.该输出信号作为自稳零放大器失调校准电路的开关时序信号,使自稳零运放的失调电压校准电路(开关电容结构)的开关动作具有随机化特征,产生的开关毛刺类似随机噪声,改善了自稳零放大器失调电压的校准效果.该伪随机信号发生器电路采用0.5μm CMOS工艺实现.仿真结果表明,该信号发生器电路实现产生的输出信号的频率在2kHz到4kHz范围内随机变化.将其用于自稳零运算放大器的失调电压校准中,自稳零运放输出信号中的谐波显著降低.

A pseudo-random signal generator circuit for auto-zero operational amplifiers is proposed.The circuit combines linear feedback shift register and multi-stage counter to realize the function of random change of output signal frequency within a certain range.The multi-stage counter is set by using the 7-bit pseudo-random code generated by the 7-stage linear feedback shift register,and the counter starts to count in the set state.When the counter is full,the output signal transitions once.At the same time,the linear feedback shift register generates a new pseudo-random code to reset the counter circuit,and the counter counts again.Finally,an output signal whose frequency varies randomly within a certain range is generated.The output signal is used as the switching timing signal of the auto-zero amplifier offset calibration circuit,so that the switching action of the auto-zero op amp's offset voltage calibration circuit(switched capacitor structure)has randomization characteristics,and the generated switching glitch is similar to random noise,which improves the Calibration effect of autozero amplifier offset voltage.The pseudo-random signal generator circuit is realized by 0.5 pm CMOS process.The simulation results show that the frequency of the output signal generated by the signal generator circuit varies randomly in the range of 2 kHz to 4 kHz.Using it for offset voltage calibration of auto-zero op amps,the harmonics in the auto-zero op amp output signal are significantly reduced.