Effectively Designing In-Amps
Conventionally, in-amps have been powered by dual polarity power sources as these allow for negative and positive input and output swings. Modern in-amps however, are expected to be functional through single power supplies as most data acquisition systems run on a single low voltage supply. Embedding single supply in-amps can be more effective as they can regulate output to within 0.5 V of the supply and within 0.1 V above ground.
Designers often forget about amplifier headroom when it comes to single-supply in-amps. Good quality in-amps can be compared to single-supply in-amps, and dual supply in-amps have an output swing within 2V of either rail.
Often designers also overlook power supply decoupling. Ideally, most in-amps’ regulators must linked to one or both power supply lines and must be decoupled depending on the output reference terminal. Every chip must have a bypass connector between each of the power supply pins and the point where the in-amp’s reference terminal is connected.
Many other factors play a role in designing a good in-amp module. These include coupling, headroom, reference input, cable termination, accuracy, and external and internal protection. All of these must be taken into consideration while designing an in-amp.