ISOLATION CIRCUITS???

Hello William,

Like most semiconductor based amplifiers the INA129 instrumentation amplifier does not provide galvanic isolation between the input and output. An isolation amplifier is requiredwhen the input and output stages of the amplifier must be galvanically isolated. Since they are isolated their ground reference may be offset by hundreds, or thousands, of volts. An example of an isolation amplifier that uses a capacitive barrier to achieve the port-to-port isolation is TI's ISO124. The data-sheet can be found here:

http://focus.ti.com/docs/prod/folders/print/iso124.html

Note that isolation products may or may not be authorized for life support applications. Here is information about the subject from the ISO124 data-sheet:

"TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications."

I am not sure if this would be an issue for electromyography, but before you employ an isolation amplifier in your application make sure that it can be used safely.

Regards, Thomas

PA - Linear Product  Applications Engineering