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Interfacing current transformer

Other Parts Discussed in Thread: LM324, LMV324, LMV344

I am Designing a interfacing circuit with Current transformer (turn ratio is 1:1667) burden resistor of 47ohm, using a Difference amplifier at the output (as my system is not having -ve supply)

OPAMP LM324 is powered with 3.3V DC. 

Voltage at +ve terminal of OPamp is a resistior divider with DC value of 0.817V.

 Gain of opamp is set with unity.

When the input current is set around 15A at primary of CT then at output +ve side there is a clipping in waveform. (no cliiping in -ve side waveform) please tell me what should be the reason for it. As if opamp saturates then both side waveform should clips.

The clipping increases when current increase further. no cliiping in negative side observed.

  • Manish,

    It is a bit difficult to use LM324 at 3.3V VCC. The input common mode range (0 to 70C) is 0V to 1.6V (VCC-1.7V).

    The output common mode range while sourcing current is 0V to 1.6V  (VCC-1.7V).

    The output common mode range while sinking more than 12uA [to 50uA] current is more than 0.6V to VCC.

    This blog has more detail

    LMV324 (low voltage version of LM324) has a better input common mode range and a rail to rail output. 
    LMV344 for even better performance.