Hello everyone!

This is my first post here, so please forgive me for any mistakes or inconveniences.

I’m currently exploring the AD8233 signal conditioning block to use in an sEMG application, and I came across its instrumentation amplifier design, which uses two transconductance amplifiers (GM) and two op-amps configured as high-pass filters to eliminate DC offsets.

I’m finding it quite challenging to understand exactly how this circuit functions, and I would greatly appreciate it if someone could help explain it.

Specifically, I’m trying to understand how the op-amp with the capacitor C1 works together with the HPA. How does the feedback through GM2 generate a proportional current to effectively eliminate DC offsets?

I’ve attached an image of the circuit and included the datasheet for reference.

Thank you very much in advance for any insights!



https://www.analog.com/media/en/technical-documentation/data-sheets/ad8233.pdf

 

I see no transconductance amplifiers within the AD8233 signal conditioning block, but rather an actual instrumentation amplifier. THAT will make the analysis a bit simpler.

 

I see no transconductance amplifiers within the AD8233 signal conditioning block, but rather an actual instrumentation amplifier. THAT will make the analysis a bit simpler.

Sorry, but I would like to understand the root of the configuration. It is pure curiosity, and I am sure that understanding this configuration will be regarding and full of insight.

However, could you explain how the R and C in pins A4 and B4 have an impact on the IA?


Thanks,

 

According to the explanation in the data sheet, past the page where your first diagram is from, the R and C values affect the Hi Pass filter response. That is explained in some detail in those paragraphs.

 

According to the explanation in the data sheet, past the page where your first diagram is from, the R and C values affect the Hi Pass filter response. That is explained in some detail in those paragraphs.

I know the explanation is in the datasheet...; however, there are some concepts I’m struggling to fully understand, especially regarding the configuration of GM2 and its real-time functionality. I’m hoping to find someone with the willingness to explain this to me in detail

 

I went back and read the complete description. The G2 amplifier gets both DC feedback and the high pass filtered noise signals, to subtract from the G1 output.
So basically it is magic.