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Differential amplifier's reference pin with an integrator amplifier ???

Carlos Ignacio Sarmiento
Prodigy 20 points
Other Parts Discussed in Thread: INA132

Hi, I've seen in some circuits an integrator amplifier's output connected to the reference electrode of a differential amplifier (INA132). I'm recently designing a EEG amplifier for neurofeedback therapies, so I need the most accuracy as posible. Explanations I've readed in some papers tell me that the integrator in that circuit acts as a natural high-pass filter and makes a high stability level to my output. MY QUESTION IS HOW CAN I FUNDAMENT THAT MATHEMATICALLY? WHAT IS THE TRANSFER FUNCTION OF THAT SYSTEM?? IS IT NECCESARY TO CONNECT A VOLTAGE SOURCE IN INTEGRATOR AMPLIFIER'S NON-INVERTER PIN (SPANadc... I supose offset)??

Thank you

  • 0
    Guru 21975 points

    Carlos,

    This type of circuit produces a single-pole high-pass function like simple R-C coupling. The roll-off frequency is equal to the unity-gain frequency response through the integrator and the output reference node of the difference amplifier. In this case, it is just 1/(2*pi*R5*C1). The roll-off is at 159 Hz with the values shown below.

    Regards, Bruce.