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Precision amplifier for DC amplifier

Ohad Bonneh
Prodigy 630 points
Other Parts Discussed in Thread: OP07, TLV2470, TLV333, OPA396

I am looking for a precision amplifier that can support the following conditions:

 

Vin: 5mV – 10mV (DC Voltage)

Single supply of 3.3V.

Vout: ~0.5V.

The voltage ripple (p-p 250uV) will be in 60Hz.

Cheap and small.

 

This gpamp is intended to a disposable medical device and we are looking to have 100ku/year starting 2023.

 

I found out these two:

OP07CDR

TLV2470CDBVR

 

 

What is you opinion? Do you have a better recommendation?

  • 0
    Guru 140200 points

    Hi Ohad,

    can you tell more about your application? Can you show a schematic?

    You say the input voltage is 5...10mV and the output voltage 0.5V. Do you mean the circuit has a DC gain of 0.5V / 5mV = 100?

    What do you mean by the 60Hz voltage ripple? Is a 250µVpp 60Hz ripple superimposed to the DC input signal? Shall it also be amplified? Or shall it be suppressed? Or shall the circuit give a noise lower than 250µVpp at 60Hz at the output?

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 22471 points

    Hey Ohad,

    Additionally, what offset voltage are you comfortable with? If your gain is 100, your offset voltage can end up making up a substantial portion of your signal.

    If you need something more precise we can move this inquiry to the precision amplifiers team.

    Best,
    Jerry

  • 0
    TI__Prodigy 630 points
    As you said, the circuit should have a DC gain of A=100 (appr.)
    The DC voltage before the amplifying will be with 0.25mV ripple p-p and the ripple will be in 60Hz (AC on DC).
    The ripple should be amplifying as less as possible.
     
     
  • 0 in reply to Ohad Bonneh
    TI__Mastermind 22471 points

    Ohad,

    I think I would recommend a precision device, I will reassign your thread to the precision amplifiers team who can help you in finding an amplifier.

    Best,
    Jerry

  • +1 in reply to Jerry Madalvanos
    TI__Genius 10680 points

    Hi Ohad,

    The OP07 is a good, low-cost amplifier, but does have limited input and output range capability (input common mode needs to be 2 V higher than Vcc-).  Depending on the input common-mode voltage, it may not work.  Typically, for operation at 3.3 V, a wider common mode input range is required, however this depends on the circuit configuration.

    The TLV2470 has higher offset voltages (2.2 mV/1.6 mV), this would yield substantial error with a 5 mV signal.

    In order to maintain < 1% error for an input signal of 5 mV, I would recommend an amplifier with VOS < 50 uV, and rail-to-rail inputs.  A couple of devices that would be a good fit are TLV333 and OPA396.  The TLV333 is a chopper-stabilized amplifier, which yields excellent offset and drift, but may show some noise "spikes" at the chopping frequency if it is used with high impedances (> 100 kOhm) for the input signal and feedback.  The OPA396 is a linear amp., meaning there is no switching occurring internally in the amp., however offset and drift is not as low.  The TLV387 is also a lower-cost chopper-stabilized amplifier with wider bandwidth than TLV333.  The OPA397 will offer a higher bandwidth than OPA396, for a good price point at this performance level.

    I hope this helps narrow the selection.

    Regards,
    Mike

  • 0 in reply to Michael Hartshorne
    TI__Prodigy 630 points

    Many thanks for the thorough answer! 
    Helped a lot