Friday, February 15, 2013

Introduce an IN-AMPS (Instrumentation Amplifiers)

In design some instrumentation for physics study, we know what we called Operational Amplifiers or OP-AMPS. But, in this article we would rather talk about the Instrumentation Amplifiers or IN-AMPS.

Instrumentation amplifiers or IN-AMPS are used in many applications, from motor control to data acquisition to automotive. An instrumentation amplifier is a closed-loop gain block that has a differential input and an output which is single-ended with respect to a reference terminal. It is not like OP-AMPS, for which closed-loop gain is determined by external resistors connected between its inverting input and its output, an IN-AMPS employs internal feedback resistor network that is isolated from its signal input terminals.


Most Commonly, the impedances of the two input terminals are balanced and have high values, typically arround 1000000000 ohms, or bigger than that. Usually the input bias currents should also be low, typically arround 1 nanoampere to 50 nanoamperes.

Gambar. In Addition, a constant direct current voltage is also present on both lines. The typical IN-AMPS when sensing a signal, the bridge resistor values change, unbalancing the bridge and causing a change in differential voltage across the bridge. On the picture, the direct current voltage will normally be equal or common mode on both input lines in order primary function.

Reference
A Designer`s Guide to Instrumentation Amplifiers 3rd Edition by Charles Kitchin and Lew Counts

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