OPA2192: unused pins

Morning Ohashi-san, 

Bruce Trump dealt with this issue very nicely, 

https://e2e.ti.com/blogs_/archives/b/thesignal/posts/the-unused-op-amp-what-to-do

In general, in most cases the best is to configure the unused op amp in a follower (buffer) configuration and drive the input to mid-supply (e.g. with resistive 1:1 divider).  The only exception is if the mid-supply would violate the op amp's input or output linear range due to low supply voltage being used - in such case you may have to drive the input with different than 1:1 divider to where input and output are within their linear range.  Having said that, Bruce's blog is a good one.