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Design help regarding translating or scaling voltage from micro voltage to Voltage

Vihang Waze79
Prodigy 50 points
Other Parts Discussed in Thread: OPA333, OPA391

Hi,

We want help regarding a design where we have to amplify a DAC output to a large voltage level

We are getting a analog voltage output from a 12-bit DAC port of our micro-controller. The analog output voltage range is 0V to 1.8V. As per the 12-bit DAC, the minimum LSB voltage is 1.8/4096= 439uV and maximum voltage is 1.8V

Now we want to scale up or translate the DAC voltage range from (439uV --- 1.8V )  to   (800uV----- 3.3V).

Since the DAC output voltages are in micro volts we are bit confused whether to use a general pupose or any instrumentation amplifier

Can you share any suitable application design which can perform above scaling up or translation of voltage range?

Regards,

Vihang Waze

Senior Engineer 

Tata Elxsi Limited, Pune, INDIA

  • 0
    Guru 262430 points

    For how to design a non-inverting amplifier, see Non-inverting amplifier circuit.

    Here is a search for 3.3 V rail-to-rail opamps with an input offset error of no more than 150 µV: ti.com/amplifier-circuit/op-amps/precision/products.html#78=In&2max=0.002:0.15&1261min=1.6:3.3

  • 0
    TI__Expert 4140 points

    Hi Vihang,

    First, I would recommend taking a look at this document. It goes over a relatively easy process of designing your circuit using a single amplifier.

    By following the equations and assuming a VREF of 1.8 V, I made the circuit below.


    As you can see, the output was very similar to what you are looking for, though dealing with uV scaling/shifting is greatly affected by resistor tolerances.

    When choosing a precision amplifier for this application, I recommend choosing one with a very low offset voltage since you are dealing with uV, that is rail to rail to simplify the supplies.
    The search that Clemens provided is good for a variety of precision requirements.

    I recommend the OPA333 or OPA391. The OPA333 is more accurate, with a max offset error of 10 uV at room temperature, but has a lower bandwidth of 350 kHz.
    The OPA391 has more offset error at 45 uV at room temperature, but it has a better bandwidth of 1 MHz. Both come in small and efficient package types as well.

    Are there any specific accuracy or bandwidth requirements for your application?

    Thanks,
    Lucas