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Differential amplifier

Hello, everyone.

In the 4-20m loop circuit, taking power in signal is small, I thought about using ADA051-2 Dual OP AMP construction of differential amplifier, the attachment contains schematics, amplifying the signal to the ADUC7061 processing, diagram parameters have to be improved? I use the oscilloscope (AC ) C14 measurements to the voltage across the 20mV VPP noise ( attached figure 1), how to eliminate the noise?

Considering the sensor power changes, ADC reference source can make the sensor power source through a resistor divider get? ( Figure 2 ) I want to know that there will be what kind of impact on circuit.

Thank you

attachments.zip
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  • Hello abcdoaabc,

     

    This is what I understand from your reply:

    1. You are designing a 4-20mA loop powered system.

    2. Power is obtained using a MAX1615 LDO.

    3. You have a bridge sensor connected to a discrete differential amplifier built using AD4051-2.

    4. You are observing 20mVpp noise at the output.

    5. You want to use a voltage divider to generate reference voltage for youe ADC.

     

    Is my understanding correct ? I would like you to answer the following:

     

    Is the captured noise differential ? or is it on one of the AD4051-2 output pins wrt GND ?

     

    Are you getting a clean power supply at the output of the LDO ?

     

    Regards,

     

    Jayant


Reply
  • Hello abcdoaabc,

     

    This is what I understand from your reply:

    1. You are designing a 4-20mA loop powered system.

    2. Power is obtained using a MAX1615 LDO.

    3. You have a bridge sensor connected to a discrete differential amplifier built using AD4051-2.

    4. You are observing 20mVpp noise at the output.

    5. You want to use a voltage divider to generate reference voltage for youe ADC.

     

    Is my understanding correct ? I would like you to answer the following:

     

    Is the captured noise differential ? or is it on one of the AD4051-2 output pins wrt GND ?

     

    Are you getting a clean power supply at the output of the LDO ?

     

    Regards,

     

    Jayant


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