如何利用5LP内部可编程增益放大器来有效地实现放大器

你好，
我想把雷达传感器连接到5LP。输出信号将是（或多或少）正弦信号，其中频率决定物体的速度，振幅反映给定物体反射多少能量。
传感器的应用说明应使用增益为70~80dB（～3100～10K）的放大器电路。参考电路使用两个放大器级，增益为100和45，因此总增益为4500。这些阶段被实现为低通滤波器。电路的输入和放大器级之间的连接是交流耦合的。
现在，我想知道如何利用5LP内部可编程增益放大器来有效地实现放大器。我的目标是将信号输入ADC并在其上运行FFT。如果有东西靠近传感器，我想使用PGA来避免饱和，这样我就可以减少增益。
PSOC 5LP PGA的最大增益为50，所以我将使用其中的三个从参考电路进入10K范围。因此，第一个问题是关于PGA的连接：参考电路放大器由反相输入端馈送，而非反相输入保持在VDD／2上。PSoC的PGA电路符号似乎使用非反相输入作为信号源（VIN）和参考电压（VREF）的反相输入，反映与参考电路相反的非反相放大器。有什么不足之处吗？
第二个问题：我将通过外部电容保持PGA之间的交流耦合，但我认为我可以跳过用于低通滤波（电容器输出和输入之间的电容）的电容器，并通过软件来制作LPF，这样行吗？
当做，
拉尔夫



     以下为原文
  Hi,
     
    I want to connect a radar sensor to a 5LP. The output signal will be a (more or less) sinusoidal signal, where the frequency determines the speed of the object, the amplitude reflects how much energy is reflected by a given object.
    The application note for the sensor states that an amplifier circuit with a gain of ~70-80dB (~3100 to 10k) should be used (. The reference circuit uses two amplifier stages with gains of 100 and 45, so total gain is 4500. The stages are implemented as low pass filters. Input to the circuit and connection between the amplifier stages is AC coupled.
     
    Now, I wonder how to implement the amplifier effectively with the 5LP's internal programmable gain OpAmps. My goal is to feed the signal into a ADC and run a FFT over it. I want to use the PGAs to avoid saturation if something is really close to the sensor, so I can reduce the gain.
    Maximum gain of a PSoC 5LP PGA is 50, so I'd use three of them to get into the 10k range from the reference circuit. So, the first question is about connecting the PGAs: the reference circuit amplifiers are fed by the inverting input, and the non-inverting input is kept on VDD/2. The PGA circuit symbol of PSoC seems to use the non-inverting input as signal source (Vin) and the inverting input for the reference voltage (Vref), reflecting a non-inverting amplifier opposite to the reference circuit. Are there any disadvantages to be expected?
    Second question: I'll keep the AC coupling between the PGAs by external capacitors, but I think I can skip the capacitors used for low-pass filtering (capacitor between OpAmp output and input) and make the LPF by software, would this work?
     
    Regards,
     
    Ralf