Hello Sir,

I try to use AD8495 with x2 Gain OP-Amplifier circuit to replace AD595. All these circuit need to be powered by single +12V Source.

Is any anything important that need to be considered? for examle, the REF pin setting and SENSE Pin Setting???

How about the linearity of AD8495 (after amplify with x 2 Gain) will be close to AD595 does or totally the same with each other???

Thanks in advance for your feedback!

Hello Stevencli,

I'm glad to hear that you're looking at our new parts. Both of these amplifiers are very linear, but they amplify the signal from the thermocouple, which is slightly nonlinear vs temperature. The transfer function of the AD8495 was actually adjusted to provide a wider temperature range with lower error than the AD595. See AN-1087 for some more information. It also has a much tighter gain error specification so that it doesn't vary from that transfer function as much.

Otherwise, assuming your gain of 2 is perfect, the connections to the thermocouple and the results will be very similar between the two solutions. If the op-amp and its gain resistors drift with temperature, then that will introduce additional errors to the system. The AD8495 datasheet shows the standard configuration in figure 33, so you can check it. Let me know if you come up with any additional questions from that.

For your convenience, here is a graph of the thermocouple nonlinearity error vs temperature of both of these solutions (AD8495*2 and AD595) so that you can compare. I generated it with the K-type thermocouple table and the datasheet transfer function of each part. As you can see, the AD8495 has less error over the entire range. I put the error in °C, but you could change it to mV by multiplying the y-axis by 10.

Let me know if you have any more questions.

Regards,

Scott