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TIDA-01421: Differential Amplifier for DC-Bias Adjustment

Ivy Jin
Intellectual 2365 points
Part Number: TIDA-01421

Hi team，

I have a question, could you please help comments?

Why the differential amplifier can filter the inrush current. 

Thanks a lot!

  • 0
    TI__Genius 17567 points

    Hello Ivy, 

    Please refer to section 2.3.4 of TIDA-01421 for the theory: "This low-speed, high-amplitude current spike is removed from the signal with the unique use of a differential amplifier stage. The output of the band-pass filter is used for both the positive and negative inputs of the amplifier, but one side of the amplifier is very slightly filtered with a low-pass RC filter. This small RC filter causes a very slight phase shift and attenuation of the ripple signal, but has very little effect on the large DC-bias spike. The common mode essentially stays the same on both inputs and is negated by the amplifier. The phase and amplitude difference between the AC signals on both inputs leads to a differential output retaining the ripple frequency component. A very large differential gain of 55 V/V provides a large signal swing of the signal difference and a DC re-biasing around 2.5 V allows the output of this stage to have a very clean and consistent bias point for the signal being measured by the comparator."

    All the best,
    Carolina