I'am working with HB100 doppler sensor and I tried to build the amplifier shown in the datasheet of HB100. This amplifier uses opamp LM324, I don't know why it doesn't work. The Vout of the circuit is always at 2.5V and the Vout of the first opamp is alway on a fixed value. I have attached the schematic and layout of my circuit, someone could help me? What I'am doing wrong? I understand that LM324 is not the best way to amplify the IF signal of HB100, but at least I should see a signal at the output! Thanks.
The currents through polarized capacitors may drive the feedback current of 1 Million ohms to rail. And input bias currents thru 330Kohm may move stage1 Vout to be well away from VDD/2, putting a large bias voltage (of wrong polarity) across that DCblock cap between stages.
Do you need R5 to be 330 Kohms? make R5 10 or 100X smaller.
And what thermal noise floor would you like?