基于STM32的流式细胞仪基线自恢复程控放大电路设计

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针对流式细胞仪在信号放大时不同增益系数存在不同基线电压,导致信噪比降低、采样动态范围下降的问题,设计了基于STM32的基线电平自恢复程控放大电路。分析了基线电压产生原因,通过STM32控制多路复用器及运放实现了各种增益信号的放大,利用乘法器DAC实现信号衰减,STM32的A/D和D/A转换与数字开关及运放的结合实现基线电压的去除。经电路设计及实验验证,系统能实现基线电压小于1.2 mV情况下5 MHz带宽信号的±40 dB增益调节,增益为40 dB时,信噪比可达 72 dB ,满足流式细胞仪信号采集要求。

Aiming at the problem that there are different baseline voltages when the signal of flow cytometry was amplified at different gain coefficients,resulting in the decrease of SNR and the decrease of sampling dynamic range,a programmable amplification circuit based on STM32 for baseline level self-recovery was designed.The cause of the baseline voltage was analyzed.By means of multiplexer and operational amplifiers controlled by STM32,various gain signals were amplified,multiplier DAC was used to achieve the signal attenuation,combined with STM32 A/D and D/A conversion and the digital switch and amplifier to achieve removal of baseline voltage.The system can achieve the ±40 dB gain adjustment of 5 MHz bandwidth signal when the baseline voltage is less than 1.2 mV.When the gain is 40 dB,the signal-to-noise ratio can reach 72 dB,which satisfies the signal acquisition requirements of the flow cytometry.