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LMP2232: amplifier structure question, Auto-zeroing(Chopper) or not?

nestor lee
Intellectual 985 points
Part Number: LMP2232
Other Parts Discussed in Thread: OPA188, LMP2234, LMP2231,

Hi TI Experts,

Can you tell me if this amplifier LMP223x is auto-zero device implementing a chopper scheme?

We have a customer designing a noise sensitive sensor, and would like to avoid using a chopping amplifier.

Thanks.

Below is the Functional Block Diagram from a auto-zeroing device OPA188

  • 0
    TI__Guru* 93105 points
    Hi Nestor,

    Usually, chopper op amp datasheet indicate when that is the case. I reviewed the details of the datasheet for the LMP2231/LMP2232 and LMP2234, and there is nothing in the specifications that would indicate that it is a chopper design.

    For example, the LMP2231 datasheet in Fig. 47, Input Voltage Noise vs. Frequency Frequency, shows that the amplifier doesn't exhibits a 1/f noise region. That noise is aliased to the chopper frequency in a chopper op amp and wouldn't show in a noise vs frequency plot. Another indicator is the very low input bias current which is typically about 20 fA at room temperature for the LMP2231. That isn't the case for present day choppers; it is considerably higher for them.

    Regards, Thomas
    Precision Amplifiers Applications Engineering
  • 0
    TI__Mastermind 49966 points
    Hi Nestor,

    No. It is NOT a chopper/Auto Zero input

    The LMP2232 is a conventionally trimmed CMOS input stage and was designed for use with high impedance sensors.
  • 0 in reply to Paul Grohe
    Intellectual 985 points
    Hi Thomas, Paul,

    Thanks for your explanation.