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Using PGA117 as a thermocouple amplifier

Other Parts Discussed in Thread: PGA117, PGA281, PGA280

Hello,

Can someone suggest a suitable circuit for using PGA117 as a thermocouple amplifier. The input may go down to

-10mV. Will a bias on Vref pin and connecting the T/C between Vref and an input channel accomplish this (Do I need to,or can simply connect it between the channel and Gnd once Vref is biased .). Is it safe to connect Vref point to the TC cable from the noise perspective.

Regards

Nikhil

  • Hello Nikhil,

    If you simply want to add a DC offset of the PGA117 output voltage, then you could apply a reference voltage to the VREF pin and connect one end of the thermocouple to an input channel. However, since the PGA117 is a single-ended device, you wouldn't be able to make a meaningful temperature measurement unless your thermocouple was measuring the temperature difference between some object and the GND copper plane. Is this the case?

    If I may suggest an alternative, I think the PGA281 or PGA280 could be a better choice for a thermocouple application. The fully differential inputs and outputs would better mate with your small-signal thermocouple input and you would get the benefit of improved noise rejection. These devices have a very wide input voltage range and also allow for DC offset shift with a VOCM input pin.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps