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TLC2654: Can't have a zero output offset from an input with 1.6 dc offset

Essa Alqudaihi
Prodigy 20 points

Part Number: TLC2654
Other Parts Discussed in Thread: OPA189

Can't have a zero output offset from an input with 1.6 dc offset. I connected the positive input to ground and the negative input to my source. the signal is amplified correctly but the DC offset is not removed and amplified also.

  • 0
    TI__Guru* 93105 points

    Hello Essa,

    Can you share your TLC2654 circuit schematic? Please indicate supply and input voltage levels, and output load conditions.

    Thanks, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 20 points

    Hello Thomas, 

    Thank you for your response. 

    The connections are as in the figure bellow. 

    The voltage supply for TLC2654 is +5V and -5V as shown. 

    The original input source is ADXL335 sensor (accelerometer) which gives you a DC of 1.65V at zero-g, plus an AC component. Basically, the output of the sensor would be between 0.75V-2.55V.

    I have tried a sinusoidal  input with a DC component as well. In both cases, the output of TLC2654 has a DC component. 

  • 0 in reply to Essa Alqudaihi
    TI__Guru* 93105 points

    Hi Essa,

    If your drawing is correct the TLC2654 CXA and CXB common connection point at pin 8 needs to be connected to pin 7, VDD-. 

    Do note that the TLC2654 is a legacy chopper-stabilized op amp. It was introduced in the 1980s. If you are working on a new design, the modern chopper op amps provide much high performance and lower noise than the TLC2654. For example see the OPA189:

    http://www.ti.com/lit/ds/symlink/opa189.pdf

    And they don't require external storage capacitors.

    Regards, Thomas

    Precision Amplifiers Applications Engineering