The demise of the Tektronix 7A22 diff-amp, and the fact that we’ve cobbled together

various versions of this long out of production device over the years, to get

our work done, tells us there may be room for a modern differential amplifier.

Our aim is to power it off USB, provide a nice ’slideback’ stable low noise DC voltage,

so that you can watch your circuit drift slowly, and learn something.