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系统实现了10 mV的微弱信号的程控放大和程控高低通滤波,其中程控放大利用AD620放大器和LF351实现两级增益放大,用6个继电器控制反馈电阻实现输出增益0 dB到60 dB可调;放大信号通过低通或者高通电压控制电压源(VCVS)滤波器,滤波器的截止频率从1 kHz到20 kHz可调。系统以MEGA16为控制核心,用继电器实现硬件电路的切换从而使增益可调,并设计了一个通带为50 kHz的四阶椭圆低通滤波器,滤波器的参数通过计算和PSPICE仿真结合得到,并在测试过程中修正相关参数。该系统思路简单易于实现,且各参数的误差较小。
System to achieve a weak signal of 10 mV program-controlled amplification and programmable high and low pass filter, which program-controlled amplification using AD620 amplifier and LF351 to achieve two-stage gain amplification, with 6 relay feedback resistors to achieve output gain 0 dB to 60 dB adjustable; The signal passes through a low-pass or high-pass voltage control voltage source (VCVS) filter with a cutoff frequency adjustable from 1 kHz to 20 kHz. The system uses the MEGA16 as the control core, the hardware circuits are switched by the relay to make the gain adjustable, and a fourth-order elliptic low-pass filter with a passband of 50 kHz is designed. The parameters of the filter are obtained by combining the calculation with the PSPICE simulation, And in the testing process to amend the relevant parameters. The system idea is simple and easy to implement, and the error of each parameter is small.