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LMP91000: LMP91000 Potentiostat Circuitry confusion

HARI T O1
Expert 1645 points
Part Number: LMP91000

Tool/software:

Hiii Team,

I am going through the datasheet of LMP91000.The functional block diagram is given below.

In page no 13 7.3 Feature Description --> 7.3.1 Potentiostat Circuitry.The below statement is given.

The core of the LMP91000 is a potentiostat circuit. It consists of a differential input amplifier used to compare the potential between the working and reference electrodes to a required working bias potential (set by the Variable Bias circuitry).

As per the block diagram what I understood is comparison between Reference electrode and variable bias taking place.

May I know how the comparison between working electrode and bias voltage is happening?Working electrode is connected to the input of TIA.

The next thing I need to know is,in the same section you can see the statement given below.

A Transimpedance Amplifier connected to the working electrode, is used to provide an output voltage that is proportional to the cell current. The working electrode is held at virtual ground (Internal ground) by the transimpedance amplifier.

How the working electrode is held at virtual groung?One end of the TIA is connected to WE and the other end is connected to a voltage divider.How virtual GND is obtained here.By virtual ground did they mean providing an offset to WE by a value provided by VREF DIVIDER

  • 0
    TI__Genius 12365 points

    Hari,

    The working electrode will float off the internal zero voltage, which is determined by the Vref divider. The bias voltage powers the sensor, and the RE is used for feedback compensation to A1. The WE pin is held at the reference potential of the internal zero voltage, and then the current output will vary as the sensor operates. The positive terminal of the TIA being connected to the Vref divider is what holds the WE pin at the virtual ground.

    Regards

    -Alex Thompson