I like to build ECG Front End base on the link shown below (Figure 5)
Can anyone explain to me each of the amplifiers is doing the the circuit?
I know INA326 have the gain of 5 for the input voltage.
A3 act as a band-pass filter?
From the App Note:
"The input gain of the INA326 is set to 5 via G 1 = 2R2/R G = 2(200 k Ω/80 kΩ). The 750-pF capacitor parallel to R 2 cancels resistor noise. The 3-dB frequency of the integrator A4 is set to 0.05 Hz, while the output stage around A3 provides a gain of G 2 = 1 MΩ/5 kΩ = 200. The precision voltage reference, REF3125, provides low-noise biasing of the 2.5-V bias voltage to the amplifiers and the 16-bit, 100-kSPS, SAR-ADC ADS8321.
To further reject 50/60-Hz noise, the input commonmode voltage is fed back via the amplifiers A1 and A2 to the right leg of the patient. This approach requires only a few microamps of current to significantly improve the common-mode rejection and to ensure compliance with the UL544 standard."
Regards, Neil P. Albaugh ex-Burr-Brown
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