[Essay] About the principle and calculation of the instrument AD820 (original) by shane
Into the company, to design a strain for small signal amplification product, as it relates to some of the differential amplifier, by selecting the multi-comparison, selected ADI 's AD620 instrumentation amplifier. Now I will sort out the principles and calculations of the AD620 and the same type of instrumentation as a post, and send it to share with you. If there is any error, please correct me.
Instrumentation amplifiers, like many amplification circuits, are used to amplify signals. However, the characteristics of the amplifier amplifier circuit are that the signals it measures are usually small signals in a noisy environment. The noise is usually common mode noise, so in the circuit design requirements, the circuit has a high common mode rejection ratio, and the signal is separated from the noise by the common mode rejection ratio. Therefore, the signal measured by a good instrument amplifier can achieve high precision, and has been widely used in medical equipment, data acquisition, detection and control electronics.
Most precision instrumentation amplifiers use a typical integrated three-op amp structure as shown. Through the virtual break and virtual short theory of the op amp, the relationship between the final output and the input can be calculated. (Because the post content involves some images, but I don't know how to insert the image into the post, so I have to upload the content of the post to be sent as an attachment. If you are interested, you can click on the attachment to see it.)
In addition, TI also has a product, which is INA129U, its function is almost the same as that of ADI's AD620, but because of the price and cost considerations, the AD620 is relatively cheaper. Therefore, I also recommend this chip here.