Analyzing circuit diagram for 40kHz ultrasound receiver

[eerocketman]

So I am making an amplifier circuit for a 40kHz ultrasonic receiver. I have found the dev board from AD which does something very similar to what I would like to do. However, I don't even know how to begin analyzing the circuit given. I haven't seen amplifiers in this configuration. Can someone help me analyze this circuit at a high level? I've attached the application notes and a snapshot of the particular circuit in question.

Thanks in advance!!!

[palpurul]

I think I can kind of understand why you can't begin analyzing the circuit. Do you how single supply opamps are biased? Have you ever dealt with single supply opamps in the past? If that's what you are missing once you learn how to bias single supply opamp the first 2 stages would be east to analyze. They are just gain stages with DC bias.

[0xfede]

Hi eerocketman,

This schematic consists of a two stage amplifier U8A and U8B and a squaring circuit U11.
You should try to see the circuit from another perspective: consider +5V as it is 2.5V, GND as it is -2.5V and VREF as it is 0V.
Both the amplifiers have an high pass input filter (@ around 41KHz) and a low pass filter (@ around 38KHz). The first stage is non inverting and the second is inverting.
There is an additional high pass filter (C30+R17 and C31+R18) that basically blocks all the dc components at the comparators inputs. The comparators output are paralleled (these are open-drain outputs) and pulled up by R19. When the second stage output signal exceed ~VREF+28mV or is lower than ~VREF-29mV the comparator output goes low.
To be clearer I've attached the schematic with a few comment. I have not performed a simulation but if you need it just ask.

Hope this help.

Best,
0xfede

[eerocketman]

Thank you so much for your response. I later found out that I couldnt see the familiar configurations. I redrew the circuit and rearranged some parts and it wasn't bad at all. Probably the lack of sleep getting to me!